To what?
         There  are 5 levels of Passwords to lose.  (or the very impossible Bitlocker™)
  1. BIOS (see below HP BIOS Password issues) (or fingerprint boots)
  2. Windows local login lost.
  3. Windows  7/8/10 live login only & cloud store . Thec trick, of using another admin account to change other users PW. (with pitfalls)
  4. Web passwords, (like AMAZON or EBAY,  banking, etc.,  this be the endless list...  in all cases ask THEM.
  5. EMAIL , ask your ISP internet service provider, or if using web mail ask them.  (1000's of providers and web mail sites, endless...)

In the future, write your passwords down, on thin paper and put  it in a book (random) on a known only by you page number, ("Post-it-notes" are best so they can't fall out book rattled by thieves)
For casual (non financial)Online passwords (like forums or facebook, etc) use LASTPASS.(gee it's even free) but this is useless to boot PW. (but not if you make Lastpass secure notes)
To read your Lastpass secure notes go to any working PC on earth, log in to lastpass online, and read you secure notes on topic, like this "my w10 boot PW laptop#3" and/or, my Laptop4, bios Pw)
Gee LastPass is free, why not use it , even only for this.? Login PW. only.
Store banking passwords only in your head, never write them down anywhere , not even allowing Microsoft or any browsers made to store any banking PW of any kind or even the login name or PW at banks.

 HP (and others) BIOS password resets  (see BIOS PASSWORD LOCK  photos here)
This is only complex due to so many classes of PC and 10+ or more generations of PC consumer or enterprise rated.
There are 2 classes of PC (besides Desktop/Laptops) and those are Consumer and Enterprise   (HPE.com covers the latter and is 10x more secure, TPM and Bitlocker tool)
I think the Laptops had the more advanced features first , due to the mobility factor and danger of that. My 2010  laptop has it, Elitebook. (partially)
The newer consumper PC's use back door (3 fails to a halt) Password recovery
Here are some consumer PC grade, backdoor decoder reset web sites,  Here-1, and here-2 or here-3.
Enterprise PC's (ie. Prodesk/Elitedesk,Probook,Elitebook) are more complex and most have all BIOS configurable,  security features.
Example #1: a 600G1: (or any G version#)
"Clear Password Jumper
Select ‘Honor’ to allow or ‘Ignore’ to not allow the absence of the password jumper to clear the passwords " as seen in the HP service manual. 
The clear CMOS jumper never works on  these , only the
CLR_PSWD jumper, works and only if the above setting allows it to work.
Thear are   are 4  listed ways,   ( most folks try #3 CMOS clear , or CLR_PSWD jumper , then if the PC lacks those (on the mobo) they then do the #4 Zero POWER reset) first tries.

The only reason to read the below is because  you never read your Service manual or asked HP for help) Below are GENERAL RULES:  (there are too many PCs made to have order)
  1. Enterprise PC (say a ProDesk or Elite...) has 2 ways, to reset (not counting TPM) The CLR_PSWD jumper, if this feature is turned off , you must call HP and get the SMC.BIN file to reset it.
  2. Consumer PC (Pavilion?) Backdoor RESET  (if you see halt codes this) with PW field blank hit enter 3 time,  if you see halt code, this is what I call a   BACKDOOR PC.
  3. The   CMOS MOBO JUMPER reset, (this empties out the CMOS NVRAM.  (works on most older consumer PCs and some Enterprise if this feature is enable in BIOS setting)
  4. Kill all power way(I call this the ZERO POWER method)  (All large batteries (1 or 2) from laptop pulled, AC power cord PULLED, in all cases and the CMOS RTC/NVRAM battery coin cell pulled.(wait 15min and reverse)

If your PC has TPM enabled, do not guess what to do,  Clearing the TMP key without knowing what it is (not having it written down on paper or stored somewhere) is big NO NO
The relationship of UEFI and TPM is explained super well here by IBM , in one page.(thank you  IBM !)
BIOS used to be simple, and some PC's now have up to 8 updates just for UEFI, because it was so buggy.
Some PCs like mine are 1/2 UEFI enabled, much easier to deal with; mine is year 2010 HP .  8540w  (my vacation only PC)
For most consumers it is best to keep TPM and BIOS passwords turned off,  unless working for CIA (haha) or have Data on you PC that is Secret/ designs / Art forms or other creative content that can not be lost or seen)
Before using this feature learn the Pro/Con's. The Con is, you lost the Password , now what do we do.?

HP direct intervention. (with a custom BINARY FILE SMC.BIN)   Is one cure. ( use HP chat to learn this)
This is not by accident it is by Design, you turned it on, now forgot the PassWord and you  or the thief  are now  blocked..

Examples of the newer PCs and how to deal with lost BIOS (or UEFI) passwords.

Warning do not  watch utube jerks, shorting out TPM chip pins to reset BIOS,  "the rule of electronics is never short things and for sure  things you do not UNDERSTAND"
First off enterprise PC by HP are called by 2 prefix names "PRO..." and Elite..." Probook, Prodesk and the like.  If you see those 2 words , passwords can be near impossible to reset.(lacking HP direct help)
If the CLR_PSWD jumper is missing or defeated (turned off  in BIOS settings), then you must cure it ,the hard way.

In the case of HP, ? why not just ask them first?,  Here read this page, covering how to deal with TPM chip,  in the OS and in BIOS.

I will now assume this PC is not a Backdoor PC.(consumer grade) nor will battery (zero power) resets work. (or jumper missing or DEAD)
The process is per below if the TPM chip is not enabled.
  1. The Pro/Elite book/desk PC's need a   SMC.BIN file, Binary flash program to load that, and it resets it.   Send your F10 info page per below.  (the  CLR_PSWD fails)
  2. The BIN file must match you UUID,  and will  not work on any other PC on earth !  Just your UUID matched PC works here.
  3. HP then sends instuctions on how to perform the reset. Some PCs have  HP_tools folder with SMC.BIN already there, (my guess older Enterpise PCs only)
  4. That means if you stole the PC, and the real owner reports this to HP, then you will never get the SMC file , no way. (foiled you are)
  5. The UUID is a digital form a  PC serial number that only your PC has, 100% unique. 
  6. If you don't like this feature, then don't buy Executive level notebooks or Elite/Prodesk PC, or simple turn it off. (in the cases of TPM , you need to tread lightly here,.
The BIOS PW feature  is a trap, if you failed to backup the days data, to external medium then you turn off this PC , you may never get back that days work.
The BITLOCKER feature is also a trap in the same way.
Learn to write down your Password, put the small paper (post-it notes rule here) in a book only you know, and the page only you know. (or learn to uses SECURE NOTES HERE)

To get the UUID, boot PC and hammer the F10 key and go to the BIOS INFORMATION page, it is there, on all HP PC.
Be sure  to tell HP your  full F10 page data, make , model, UUID on that F10 Page.
My newer PC 2010 , is hammer ESC then hit F1. Seen below photos.

UUID =  (HP once sure you own SAID PC, will ask this number or even as step 1) (only your PC has this unique to you, huge serial number)

A universally unique identifier is a 128-bit number used to identify information in computer systems.
3.4028236692093846346337460743177e+38  , combo's (that is in scientific notation)

The most hard of all PCs to reset the Password, requires a SCM.BIN file to be burned into the BIOS memory (a reset ) only by asking HP. (telling HP your service tag data  or all seen on the F10 page)
here; by country.
or chat


In the case of HP, ? why not just ask them first?,  Here read this page, covering how to deal with TPM chip,  in the OS and in BIOS.
MY F1 screen.

On newer HP PC's they deleted the SERVICE tag stickers, and only use the above F1 data. (so if the screen is dead, you are screwed, nice no? I call them marketing PUKES)

End BIOS issues .

Local Windows OS  Password, I will not cover all 14 versions of windows. no.
Before Hacking , backup your data first !
The best hack we are told is the linux hack, using chntpw  (change NT Password) works windows 8.1 and older. OS. (it just changes it and does not need to guess the old one first)
The offical statement from MS is to reload the OS,  (after all would they teach how to steal other persons private data? answer, no!, why would the?)
Each year the OS get more difficult.  (if running relic and dead, now, XP or VISTA use google to hack it, these old OS are child simple  easy to hack. )
  1. Didn't write it down?   oops1
  2. Did you make a password recovery disk,  day 1,?  no? oops2.
  3. Now are you going to reInstall the OS? no? (the MS offical way)  HP F11 key fixes this, HP recovery 2006 to today.
  4. We land squarely on hacking. I will assume w7 or newer. (XP is dead and a virus magnet.)
Windows 7 HACK.  (no virus way is " copy d:\windows\system32\utilman.exe d:\" A.K.A; the login page, exploit !
W7 has  login screen exploit that allows manual hacking of 1 file to get ADMIN (cured in later releases, dig?)

W8 near same as above.

In all cases Ask Microsoft.com first for help,  if they say, reload the OS then there you go, and most pages at MS say just that.

Next is: (local login's)

W10 , after many updates and newer builds can be very hard to hack , even impossible,  Some methods below are not free.
Learn one thing about W10 now, it is a moving target, at any time any day, MS can fix Password hacking methods, I say count on this.!
The W10 hack site 1:

The W10 hack site 2:

I don't do hacks, but you can learn to WEB SEARTH  it.

Keep in mind if the HDD uses the MS or HP encryption feature, I bet all the above fails...  (by design!)

The HP has F11 recovery partition that gains access to the installer and command prompt. (if you need to do that to hack)

The Microsoft home page for W10 down load will burn any DVD or stick with W10 installer,  (takes no retail COA key like W7 does, to DL it., so .... do that.)

Next time learn to write this password down on paper, and put the paper, in a book only you know, and page only you know. (I use PostIt notes so the slip of paper can not just fall out of my book)
All this is done  to protect your data,   even banking transaction data, etc...
If you can login (before) with no internet connection, then the above is true, you are local, but if you could never login, with the internet dead, then the below is what you have. (you have LIVE)

LIVE: (not local as shown above)
Rule #1, only microsoft can help you here, nobody else can hack microsoft online servers.  For sure not you.
The Microsoft live login , (if you said yes during the install of W10 then you are using  the Microsoft LIVE CLOUD login,  to reset that , as millions have is there.)

Cured only by going to microsoft live and doing  request there.                       And this MS policy page.
If these answers on the above line fail you must call microsoft on the telephone (Cell phone/CELL) and ask for help. (be ready to pay CASH)
  • In the USA, (800) MICROSOFT (642-7676)
  • In Canada, call (877)568-2495
  • In India, contact 0008004402130
  • In UK, contact 0800 026 03 30
 The below is fake  live.com login, only you know your, live email login password.  (next time write it down in a secret place only you know, hide it in a book? only you know and page #?) 

Microsoft has many older live login ways, hotmail, office login's and Xbox 360 login's.
Commonly it can be your  hotmail.com, live.com, webtv.com, msn.com, or other Microsoft-provided email address is already your Microsoft account.
Even owners with Office 365, have an office email account that can work as the W10 login.
Do you use the Microsoft Store [y/n]?  if yes you  have an  account there at Microsoft.
Do you use the Microsoft Cloud? same deal as the store.

Only you know how you login, like see above, it is live.com (or the MS cloud login)
The MS page on this is here.(the CAN'T LOGIN PAGE)

Next time learn to write this password down on paper, and put the paper, in a book only you know, and page only you know. (I use PostIt notes so the slip of paper can not just fall out of my book)

Here is set of failed login password screens,  a running list of all possible screens, on topic.
W7,  login,  you can have say 5 or more users here, with there own ICONS , and own PW. 
The solutions are only 3,guess all day, reload W7 from scratch or go online and find hackers that can hack it, and it can be hacked.

Here next up, is the BIOS password lock screen. 
This happens at power on , way before WINDOWS anything ever happens.  (super old PCs had  a PW or CMOS reset jumper clip on the motherboard, hint, read you service manual, it shows how to do that)
To hack this on older PCs there is a back door PW sold or go to HP.com and ask them, get it for free,  when you guess wrong 3 times, thie screen shows an unlock code, give that to the hackers or to HP.com for the new PW.
If you get no Halt , codes, at all, then that means you must contact HP (or your OEM) directly.
On all newer PC (TPM or UEFI) 2008+ you need to ask HP. Fixed it by contacting HP support and using (flashing BIOS with) customized SCM.BIN file.
No lie the very old PCs 2000 to 2008 years, pulling all 3 power sources from PC resets this.

Bitlocker, locked. (this too happens before Windows does squat.  (if you get this one below and lost the PW you are toast.  you will not break the 256bit AES encryption here.) (sure you can guess )
On paper, 2256 may seem like a normal number, but don’t you dare underestimate its power.(ti.com calculator shows, 2 to 256 power is 1.16-E77 decimal combo's.  Below is unrounded number)
 256-bit will have 115,792,089,237,316,195,423,570,985,008,687,907,853,269,984,665,640,564,039,457,584,007,913,129,639,936 (78 digits) possible combinations.
No Super Computer on the face of this earth can crack this. it will take millions of years to do so.  (not saying if you got one PW letter wrong say  L is l and bingo works. ok?)
Do not think for a moment the software below  lets you gets 10,000 times a second, IT DOES NOT.
Aka, HDD encryption.  Some newer HDD do this inside the HDD itself, and is not crackable by design.
Notwithstanding, say your Bitlocker PW was your moms maiden name,  say it's "lovelace",   and you got 1 letter wrong case. It only takes 8 tries to guess it. (1 of 8)
If you don't know the PW name at all, (clueless) or letter counts,then guessing is IMPOSSIBLE HERE.
Like this doozy from Lastpass ($&A3PiX9G1#qEW5xHLkB) I use similar... and I do love lastpass.com (big time love) try Secure notes there !!! use it or write them down.
Btw I never write down banking PW nor Usernames at same,  all are in my head.

 This comments are only mine, and mine alone and are only OPINIONs. The real truth is all this STUFF varies by the year and make your PC .

version 2  .  8-1-2017  .   revised for more PW examples 6-20-2018