Windows Vista on logon gives error messgae "specified domain does not exist"

[bwaanaa]

Hi:

This is my niece's laptop for home use and one user only. Everything was fine for 2 years but now she cannot boot the windows. On starting up the system, instead of the normal window containing username and password screen, she gets a square window in the middle of the screen that has "other user" displayed on it. Clicking on this she gets username and password screen. Whether she puts her name and password or administrator (with or without password) she gets the message "The specified domain either does not exist or could not be contacted". There is no other option on the screen to choose a domain. This laptop is not used for office either.

I have tried booting in Safe Mode (using F8). But no matter what option you choose, repair, Safe Mode, Administrator, it always boots up with the same "other user" screen. I have tried all the options there with no success.

I tried using TRK (Trinity Rescue Kit) software package to remove the password but that didn't help. I wonder if it is virus.

Unfortunately my niece hasn't backed up the files at all so I am hesitant to reinstall the system at this stage. I am hoping you can help me resolve the problem without the need to reinstall.

Any help would be greatly appreciated.
Thank you.