Does anyone know about Win 2000?

I have a laptop with Windows 2000 on it, I basically used it for e-mail (dial up) , offsite bids and such.
I set up a wireless home network and tried to put the laptop on it using a wireless card.
The laptop worked great alone, I would put my login and passcode in and it would boot up. BUT, I changed my network settings in the laptop (computer came from a defunct telecom company) to match my home network and when I rebooted the system some security profile came on and NOW when the login screen comes on and I enter ny user name and passcode and it tells me to go cheney myself, I didn't change anything but the click from domain to workgroup in the network settings?... I don't have any disks for it or anything..

IS there any way I might be able to get into the system and change it back? or at least retrieve my info to put on another system?

Thanks