Reset password for Windows 7 for free, with no additional software

Insert either a Windows 7 installation DVD, or a Windows 7 System Repair disc into your optical drive and then restart your computer. After your computer boots from the disc or flash drive, click Next on the screen with your language and keyboard choices.

Click on the “Repair your computer” link.

Note: If you booted with a system repair disc instead of a Windows 7 installation disc or flash drive, you won’t see this link. Just move on to Step 4 below.

Wait while your Windows 7 installation is located on your computer.

Once your installation is found, take note of the drive letter found in the Location column. Most Windows 7 installations will show D: but yours may be different.

Note: While in Windows, the drive that Windows 7 is installed on is probably labeled as the C: drive. However, when booting from Windows 7 install or repair media, a hidden drive is available that usually isn’t. This drive is given the first available drive letter, probably C:, leaving the next available drive letter, probably D:, for the next drive – the one with Windows 7 installed on it.

Select Windows 7 from the Operating System list and then click the “Next” button.

From System Recovery Options, choose “Command Prompt”.

With Command Prompt now open, execute the following two commands, in this order:

copy d:\windows\system32\utilman.exe d:\

copy d:\windows\system32\cmd.exe d:\windows\system32\utilman.exe

To the Overwrite question after executing the second command, answer with Yes.

Important: If the drive that Windows 7 is installed on in your computer is not D: (Step 5), be sure to change all instances of d: in the commands above with the correct drive letter.

Remove the disc or flash drive and then restart your computer.

Once the Windows 7 logon screen appears, locate the little icon on the bottom-left of the screen that looks like a pie with a square around it and then click it!

Now that Command Prompt is open, execute the net user command as shown, replacing myusername with whatever your user name is and mypassword with whatever new password you’d like to use:

net user myusername mypassword

Tip: If your username has spaces, put double quotes around it when executing net user, as in net user “Bryan Adams” NewPasswd.

Close the Command Prompt window.

Login with your new password!

While not required, it would probably be wise to undo the hack that makes this work. If you don’t, you won’t have access to accessibiily features from the Windows 7 login screen and your computer may be subect to risk.

To reverse the changes you’ve made, repeat Steps 1 through 7 above. When you have access to Command Prompt again, execute the following:

copy d:\utilman.exe d:\windows\system32\utilman.exe

Confirm the overwrite and then restart your computer.

Important: Undoing this hack will have no impact on your new password. Whatever new password you set is still valid.

Source: pcsupport.about.com