We tend to forget our Windows administrator   password.  With no way to get into the system, you can’t even perform basic  maintenance, let alone a thorough tune-up. Formatting is always an  option, but we consider that a last resort. (Plus, guess who’s going to  have to help reinstall all the programs lost after a wipe?) But all  hope is not lost. There are a few ways to actually retrieve a lost  Windows account password. Read on, and we’ll show you the light.  
When we  install Windows , it automatically creates an account “Administrator” and sets its password to blank. So if you forgot Windows password then try this:Start system and when you see Windows Welcome screen / Login screen, press Ctrl +Alt +Del keys twice and it’ll show Classic Login box. Now type “Administrator”  (without quotes) in Username and leave Password field blank. Now press  Enter and you should be able to log in Windows. 
Now you can reset your account password from “Control Panel -> User Accounts“.Same thing can be done using Safe Mode . In Safe Mode Windows will show this in-built Administrator account in Login screen.
If you sure that you had completely no idea what your password is, then keep trying these methods.
Method 1: Take a restSometimes, human being is a little weird. You won’t get the thing  that you urgently need. So have a coffee, take a snap or even come back  after a few days, you may found that you suddenly ‘remember’ your  Windows password.
Method 2: Reset Windows password  with RESET DISK if you made before.Windows XP and  further versions also  provide another method to recover forgotten password by using “Reset  Disk”. If you created a Password Reset Disk in past, you can use that  disk to reset the password. To know more about it, please visit  following links:
http://support.microsoft.com/kb/305478
Method 3: Recover Windows password from another administrator accountIf you cannot log on to Windows by using a particular user account,  but you can log on to another account that has administrative  credentials, follow these steps on how to do the trick:
1.      Log on to Windows by using an administrator account that has  a password that you remember. You may need to start WinXP in safe mode.2.      Click Start, and then click Run.
3.      In the Open box, type “control userpasswords2“, and then click OK.
4.      Click the user account that you forgot the password for, and then click Reset Password.5.      Type a new password in both the new password and the Confirm new password boxes, and then click OK.
Method 4: TRY command prompt about password reset trick1. Log in with any valid account.
2. Bring up the command prompt.
Type: net userYou get a list of accounts
Type: net user Administrator *Type: net user (any account on that list) *
3. It prompts for a password. Enter one, then enter it again when prompted to confirm.Now, try to log on as ‘Administrator’ with your new password.
* Please note that this might not work on a LIMITED account
Method 5: Use the third part Windows password recovery tool If above solutions didn’t work, taking use of the third part utility  is the best choice. There are a lot of tools and utilities that can be  downloaded and used to recover, reset, retrieve or reveal existing  password. These windows password recovery  utilities, free or paid, are usually a Linux boot disk or CD that able  to comes with NT file system (NTFS) drivers and software that will read  the registry and rewrite the password hashes, or can brute force crack  the password for any user account including the Administrators. The  advantage is that there is no fear of leaking your password to  outsiders, while the process requires physical access to the console  and a floppy or CD drive, depending on which tool you choose. And it’s  not easy, although it always work!
Below is the most famous recovery tool I found:Windows Password Unlocker – it is the most popular Windows password  cracker . It is a very efficient implementation of windows any  versions. It comes with a Graphical User Interface  and runs on multiple platforms. Windows Password Unlocker helps to  recover Windows passwords without reinstalling or data loss. It can recover admin password for Windows 7/XP/Vista/NT/2000/2003… You can view more at Password Unlocker Official site: http://www.passwordunlocker.com/products/wpu.html
Password Unlocker Bundle  –It is a professinaol password recovery kit, which contains series of password recovery tools: Windows password recovery, PDF password recovery, MS documents password recovery, MS Excel password recovery, WinZIP/ZIP password recovery, WinRAR/RAR password recovery, MS SQL password recovery, Internet password recovery, Windows Live/MSN password recovery, MS Access password recovery, Outlook password recovery, and Outlook Express password recovery, etc. No matter you are at home or in office ,the bundle helps to reset  passwords we forgot or lost.