On one of my VMs with Windows 2008 Server, I needed to reset the Administrator password. A quick google led me to a very nice little trick. This also works for Windows Vista, Windows 7 as well as on Windows 2008 Server.
The trick involves booting from a Windows CD, getting to a repair 
Command Prompt, replacing the utilman.exe file with cmd.exe, booting Windows up as normal, and then clicking the “Ease of Access” button on the login screen to bring up a Command Prompt to issue: net user administrator newpassword
What you need to reset the Password
- A Windows installation DVD (or reinstallation DVD)
(If you have Vista installed, you’ll need a Windows Vista DVD. If you have Windows 7, you’ll need a Windows 7 Microsoft DVD).
Reset the Windows Password
Insert the Windows installation DVD- Reboot the PC and boot from CD/DVD
- Choose “Repair”. Under the Repair menu, look for “Command Prompt”.
- In the Command Prompt, issue the following commands below:
c: cd\ dir #(You should see some folders listed. If you don't see Windows, change to the d: drive. d:) cd Windows cd System32 move Utilman.exe Utilman.exe.bak copy cmd.exe Utilman.exe
- Reboot the PC and start Windows
- Click the “Ease of Access” button on the bottom left (or press Windows + U)
- In the resulting Command Prompt window, issue the folllowing:
net user administrator newpasswordhere #(to list all local usernames, just type "net user")
- Close the Command Prompt and Login 🙂
- Rename and move the files (utilman.exe) back.
Further information: youtube has many videos showing a step by step process. See: http://www.youtube.com/watch?v=Ar-VoO9ogHc
This above method helped me quickly reset the Windows Password without having to go making a special boot CD such as the Offline NT Password and Registry editor.