Everything? to know about external HDD, hard disk drive and Drive Docks.       
A.k.a  Rust drives and Spinners
The word "hard" means hard platter and not old floppy disk flex media.

See my Lightning fast cures , and diagnosis  here. (all reasons to fail and all tests and cures)  << go here first , this page covers all types of failures and all classes of Ext. HDD.
We use these devices and product below to test HDD under suspension or to back up data. (any)
The time to backup is before your main boot drive gets corrupted ! (or goes BAD)
I use AOMEI backup (free) to backup all my data or to clone any drive you want. 
The external DOCK, or enclosure, or a DOCKING STATION ,  just get this and do not read why it works below, complexity is never simple with computers. ok?
Do know that some folks avoid all this and use cloud storage.
Both  source and destination HDD must be good to copy files, and neither failing S.M.A.R.T,  tests, nor allowing either 1 or both drives to be full. (ever)
A drive may  be good , fully, just lacks a drive letter assigned by you in Disk-Manager. (or was never formatted or formatted wrong, or not NTFS)
Some drives fully scrambled can  be cured using these erase steps.
See my page on how to test suspected bad HDD here.
This  page is about all PCs working with  the best external drive enclosure or interface or dock, you can make one your self. ( or DIY  and buy the case, then buy any drive)

This first "POWER" rule does not apply to 2.5" 1TB cheap external HDD as seen here. (by WD or Seagate say sold at Target or Walmart)
This drive runs on Windows 10 with no problems and is NTFS formatted correctly NIB, new in a box.
1-TB is common cheap size. (note the lack of any kind of power pack here) Even better is any External SSD !
Most folks use this and have no problem if they use the Task bar or Explorer "EJECT" radio BUTTON. (Or do this)
Click me to zoom Easy drive.  a 2.5" disk inside.
The above drive can be S.M.A.R.T tested with free and safe.
If no fail there data can be recovered with  Recuva for free.

THOSE BIG 3.5" DRIVES.  (the case of this drive alone is  1-inch tall, 4-inches wide and 5.8" long and with enclosure  added bigger)
3.5" is the actual disk inside Diameter.

The more tricky HDD to get working is below the BIG FAST DRIVES.
2TB to 16TB 3.5" and the fastest HDD on earth in fact.

The Same 2 tests can be run on this huge drive too. Do so.
The huge drive fails for some very simple reasons.
  1. The drive is bad and fails smart tests. (all you can do is attempt to recover some data see Recuva link just above)
  2. The USB port is too weak. (most are)
  3. The external mandatory AC/DC 12vdc 2 to 3 ampere power pack is lost , missing or the wrong one. (mixed up with others , ouch)
  4. Not tried on all USB ports.
  5. Not tried on other PCs to see of bad PC is just bad in some odd way like bad USB ports. (or bad drivers on the port.
  6. Some old 10 to 15 year old HDD drive enclosures have no Windows 10 driver at all today. (get  new enclosure)
  7. Not using NTFS format and was used on MAC PC or LINUX and now fails on Windows 10. The cure is reformat the HDD.

Proof links:
The Mobile  ST2000LM007    (see  the motor  "SpinUp" current here to learn why the power pack is not optional)

ST31500341as  go as high at 2.8 amp motor startup.

USB hell: (cured using my special USB enclosure)
Vast models of PC can not ever do USB power  demands 100MA to 2amps. (only USB -C can do 2amps)
I have USB current tester and tells me in seconds what power is there,  at full load 4.6vdc minium voltage drop (from 5v) and  the current it can handle.
The wiki is some help here. See this chart, see 100mA hopeless ports?  Many External drives run fine with USB v3.  900mA is concidered minimun on most modern PC. USB -C tops the cake, at full 3amps 15watts.
USB-C can run any drive made.
Most PC made today or last 5 years can do 800mA current easy. This current will run the red Easy drive seen above.

USB 3 is super common now.
The 3.5" drive  cure is simple use only Enclosures and DOCK's with its own power pack rated 2amps or more. (SOLVED)!
or buy the BC1.2  powered hub with a 5amp power pack!

This is cheap slow 3.5" HDD that uses about 2.25 amps of motor startup current.   Many USB ports made can not run this drive. (lacking a power pack)
This is scope view of current (using a current probe )

Below is trick in windows Device Manager on some PC , that can show the actual current available on a USB port. (possible and actual both)
Motor spins up, and uses lots of current.
Here is my oldest 3.5" HDD encluser box,  that still works in windows and needs 2.0amps of power or the Drive inside will be born dead.
Do not forget to connect the 12vdc 2.0 amp or larger I used 2.5amps for my newer faster drive. Do not mix up power packs or forget to use one.

This funny trick below shows cables sold that allow you to add up 2 weak ports and get  2times the power to any HDD external.
The odd thing about PCs is that you need to stagger the 2 cable wide as most PC share power on 4 USB ports in a group.
Yes very tricky wiring inside cheaper PCs.
If each port is 500mA rated now you have 1amp to start up the motor. 
Even better is :

The great USB powered HUB.
Cured ! This HUB has  huge power pack, that powers all jacks below.  This device makes any PC used , to have at least 2 amps of power to USB devices and is FULLY 100% Active HUB (not passive at all)

ONE MORE POWER GRAPH (SCOPE VIEWED LIVE  This is for 3.5" drives only, skip these facts for 2.5" slow  drives.
The External HDD is:  The drive maker seagate used Ocillicope and a nice current probe to do this, (means it's REAL)
Seagates current 3.5" "Desktop HDD series" (runs 2 to 2.5AMP startup in red below, on the  12vdc line.
This current is huge, and power on 2.5inch  is 5watts max but this one is 30watts,  6 times more.!!! 6 Time more power is needed to spin up this large HDD.

This is an Enterprise drive:
The green line is 5vdc turning on .(the step)
 The red line is 12vd motor startup current on the  ST6000NM0235 drive.
Again these are scope views with current probe on the motor power wire. 2.52 Amps to start up motor (in red)
I hate to tell you USB can not run this drive for POWER. Unless TYPE C or better. (charger current rated USB ports may work here, I have not tried it)
ONE more SCOPE VIEW (real)

This Drive run great in my powered external case and my DOCK USB and eSTAT both work.

If power is lacking you will hear the HDD try to spin up then fail and spin down , repeats forever and is not good to run any drive like that for more than a minute or 2.

eSATA: (cable connected HDD) (some PC can even hot swap the cable setup correctly)
Some laptops do not have a 12vdc pin on the eSATA port,  making the motor dead, on any connected HDD. (unless you connect a 12vdc power pack to the drive.)

MY RECOMENDATIONS: (for Case/enclosure boxes)  I like dual sized drives and only with a full 2amp power pack or larger amps. USB3, works for cloning or backup duty)
One of my better drive DOCK's:  . Runs any drive made connected to any PC you can dream up old or new, does them all. HDD and SSD any size. (no PATA from 1999 back)
Do not leave cover closed on real HDD 3.5" or it will overheat, for sure  the fastest drives do.  Seen 60C hit not good that.
Love it.

One more is  my faster and high powered, enclosure below. (seen this on ebay.com)

ORICO 3.5 inch USB C Hard Drive Enclosure for SATA HDD Support Max 8TB UASP SATA

Runs my  SEATAGE ST6000DM001  3.5" HDD 6TB at full speeds,  200MB/s  + in fact more.  (with my new USB-c PCI-e card upgrade)
I have this fastest HDD on earth in this  box. (fastest means a real rust spinner drive not SSD hybrid jive.
Cute, does no win over function.  ( real world matters) and heat is #1.  The bad casing has not one air vent and will kill dead any 3.5" fast drive quickly.
This will overheat my fast 6TB  3.5" HDD to 60C fast, so I bored, 10 holes (1/4" bit) on the bottom and 6 on the top and use a vertical base to keep air flowing the correct way)  41C now. (20 over ambient)
the USB-C chip here is rocket FAST (love it) but hate the case I DO ! (good for SSD not for HDD)
with 12vdc 2.0amp power pack for 3.5" drives a must.
This casing Un-altered, is for SSD or old slow cool 2.5" drives.(only)  A 2TB SSD would scream in this box.
My drive is fast but overheats, due to the poor case design (plastic)
Cured:  (in truth they made the case fit razor close (top/bot) inside, making air flow near impossible..)
I drilled lots of hole and added a fan and not runs super cool. (ugly yes, fast and cool yes)
I would never do this if not for the super fast speed USB-C chip inside (a rocket it is !!!!) China are you listening.?

Nobody makes USB-C case with a fan,  and needs one for 3.5" !!!!!!. (on drives this fast and mine  is fastest HDD rust drive sold  on earth) 10watts it uses and must not be CONFINED and running at 60C ever.
6TB HDD here. "ST6nnnnnnnn"

One more device that technicans use to test or clone any 2.5" HDD.

The below only works on SSD or 2.5" HDD,  not 3.5" spinners. ever.

Tests and cures below, all.    (this device is portable / mobile making the number of causes of failure HUGE)
First up is the top 4 causes of failure  are:
  • Dropping the drive, and for sure while it is still spinning and was bumped off a desk. (cure is new HDD)
  • A bad HDD, they like to fail easy at 5 years old. (cure is new HDD)
  • The drive was used on another PC and fails in this PC, due wrong format not  NTFS like windows needs. (moved from MAC or Linux  to W10 will like to fail) Cure is reformat the HDD to NTFS.
  • Not doing the required, EJECT disk before removing this external drive first. (cure is run Checkdisk)

Now a longer list and more testing.
The USB port is dead, or all are dead, seen in device manager , the cure is getting the right drivers for your USB port and 1 more for the drive enclosure chip.

Solutions to a dead or flaky HDD external drive: Lightning fast all causes of FAILURES and all cures list for W10 only. 
This is long due to the complexity of any external HDD, (hint vast types exist, HDD in 2.5" or 3.5", SSD , or USB drives or Esata drives.) I will cover only USB.
you test the HDD USB on all USB PORTS? this is first.
Does  USB thumb drive work in all USB ports and a mouse  work on all USB ports , if yes the USB ports are not dead, so next we check USB external HDD drivers for good , bad or missing.
Did you test the HDD on a good 2nd PC to be sure the drive is not failing?
Did you lose the 3.5 inch sized HDD power pack, opps?
The drive must show up in 3 places not just one , and in this order,  Device Manager and then next in DISK Manager and for sure  last Explorer.("This PC") with a drive letter.
If missing in Device Manager that means the drive is dead USB dead  or the HDD driver (sw) is wrong or missing or none exists for W10. (I focus on W10 here) ( go to: control panel + device manager)
If ok in device manager we next look in Disk manager next, C:\Windows\System32\diskmgmt.msc (location of app) we type in the run box Diskmgmt.msc and bingo go  there. (fast way) or 7  ways seen here.
The ext. drive  must be here, if not  it is bad or fails in device manager.  If it is there it must have a drive letter, if not add one (right click drive change drive letter), or it can not show up in EXPLORER, ever.
If the ext. HDD is super old for 2001 to 2007 XP PC's  back then or VISTA , those are no good now on W10 as the maker, never published a W10  SW driver made now. SW means software here a Device DRIVER.

The larger 3.5" HDD had a power pack when new and was lost? or using the wrong one,  many drives now sold new 2.5" only, needs no power pack like Seagate's  2TB Model: STHN2000403
If the larger HDD (3.5") does not spin up the power pack is wrong or missing or the HDD is bad,  it must be heard to spin up.
If the drives does show up in Explore but fails now, we do this diskcheckup  and if failed that is a bad HDD
The HDD fails on all USB ports on 2 PCs, (both PCs windows 10, I do not do Linux here  or MAC support) nor is the drive formatted for Apple nor Linux.(reformat the drive to NTFS)
NTFS format is best for recovery,  on any Windows based PC.
If you are lucky and the HDD works but files are corrupted: We do this next.
The HDD has data that  I do not want to lose. (run
Recuva for free.)

Some relic super old LAPTOPS with USB1 spots (weak 100mA ports) that fail, I then:  (buy and use an exernal power buffer seen here for a cure.)

Most old XP , HDD external drive chassis do not run on W10 now at all lacking current drivers. See the chip I am talking about here?
The in proper order , step by tiny step  list that finds true causes of failure . (all) MS = Microsoft and CP means control panel.
Rule#1 the PC must be internet connected for Plug and Play can work (PnP).  (for sure  the  first time using any new USB device of any kind)
Best is have Windows sounds enabled, in control panel for USB , connection sounds.
  1. I plug the drive in with drive to my ear and hear it spin up after the USB ding dong sounds connection sounds, if not try it 3 times on all USB ports. (CP+sounds+sound + device connect = enabled)
  2. if not the USB port is dead or drive is dead. Some folks upgraded a PC from XP or Vista to W10 and all USB3 ports are dead, because there are no USB3 driver for this PC using W10, device manager tells you this is wrong.
  3. If you fail here test the drive on a 2nd good PC.  (must show up in 3 places, again, Device Manager and then next in DISK Manager and for sure  last Explorer..
  4. Ok it spins up , the drive motor is heard to spin, what is next is DEVICE manager. Photo#1 USB ports not dead, and Mass storage USB drive seen. (if not the PC has missing drivers or the HDD drive is dead)
  5. The drive must show  up in Device Manager, this must happen first. or per above list of facts, and needed conditions.  In control panel  (CP)you see Device manager. ( start + run , type control panel)
  6. Next is Disk manager,  See photo 2:  Drive not missing and if there, must have driver letter (E:)? if not add a drive letter now. (C: boot, D: DVD and E: external HDD.)<<< typical example.
  7. You now have a  drive letter, go to Explorer now, Start run , THIS PC , and  go to drive E: (yours may be different letter) and right click that drive, and pick properties,  and Tools, and last click CHECK (photo#3)
  8. One smart move is give the Ext. drive a volume name like USB-HDD-1, this makes find it 10x more easy.
  9. Then run MS,  CHECK here is the Microsoft free "chkdsk app" for repairing corrupted  format structures on a HDD. There are vast other tools sold that can fix the same thing.
  10. If all above fails the HDD is bad. (fails on 2 PC's !!!)  If data is not lost  buy  a new HDD, and install it.
Photos of working extenal HDD (hard disk drive)
See the word mass storage DEVICE USB?
in Disk drives if  not it is a dead drive or dead USB port. (fact) that is why tesitng on all USB ports and 2 PCs, to prove that.
Lean to EJECT the HDD External when done, if not you risk corrupting the drive. See cures here.
This cures failure to Eject errors, forever. But here is a great page on failure to eject, from PCworld.(tm)
Do not allow Windows to run indexing on any external Drive, HDD or SSD, or if doing so EJECT will fail. Close all APPS and EJECT the drive with Caching (write) turned off.
Right click the DRIVE (E:) and pick properties, and then on that page turn off allow indexing.
CASHING OFF (write):
Photo #1 (In Control Panel, I clicked Device Manager) if the line with black arrow shows, errors , here that is a bad driver for the external HDD. (W10 does not support lots of 15 year old drives external)
Do not forget to look for bad. USB ports are not dead and the external HDD shows up as seen below; 
This cures FUTURE corruption. (turns off WRITE CACHING)!!  Current corruption can be cured by doing what is seen in photo3.
This only works if drive is good,  this is before you do wrong things with the drive.  (as in new drive, formated and is E: (or what it is) and doing this makes EJECTING the drive not needed ever.)
this check mark here prevents HDD  corruption next time , unplugged before ejected.

Photo #2

Photo #3  A NTFS drive will be corrected using CHECK below, So only uses NTFS format.
In windows, right click a drive , pick properties and then tools and run the MS CHECK (of drive)

If "CHECK fails" run Recuva for free.
Cures behond this are vary clostly. ( short  of  a new HDD)

Once connected you can :
  • Drag and drop 1000's of file to the drive.
  • Backup mp3 Music  or MP4 videos here.
  • You can run backup software of vast kinds and backup to here. like AMOEI backup (free)

Diskmanager the long way there is:  Start run box , find Control panel, +, Admin tools + computer managment., + diskmanager (or 7ways here)

version 6  8-8-2017   (7-7-2020 revised)