Windows Unable to Login to Windows

I have a laptop at work that is running XP Pro and connects to a Windows 2000 Server. I needed to take the laptop off the domain, make some changes, and rejoin it to the same domain. I went into the system properties and changed it from the domain back to the typical "WORKGROUP". It then asked for the admin credentials to complete this change, which I entered. Then I rebooted, as requested by Windows. When the login screen came up, there was of course no domain for me to login to. I entered the admin user name and password, but it wouldn't let me in. I tried a blank password (the solution the last time this happened), and the old admin password. No luck. It now appears I'm locked out of the computer altogether.

Any ideas?

Thanks!

 

Take a look here

 

Didn't work. The .ISO files (I tried a couple of them) weren't valid to use as a boot disc (burned with Nero). I gave in and wiped the system. Thanks for your help anyway.