Steps to reset a Windows account password given physical access to the box:
- Boot a Linux live cd and mount C:somewhere.
- Find magnifier.exe (somewhere in System32) and replace it with cmd.exe.
- Boot to the Windows login screen.
- Press WinKey + U
- Start the magnifier, which should run cmd.exe.
- Change the password in the Command Prompt.
Note that this will destroy all data encrypted with EFS.
I'm not sure who thought of this first, but if I knew, I would credit them here.