Windows won't start

[GNS1310]

I'm using windows XP home.
Computer starts up, gets to the "Welcome/User Name" screen, I click on my user name and then it says "saving your settings" and shuts down. Well, it doesn't shut down, it just stays at the user name screen. Sometimes the screen goes blank then it says "logging off" then goes back to the user name screen.
I've tried to start in safe mode then log in to the admin, safe mode with command prompt and it just does the same thing.
Good thing the laptop is up and running!

 

[Matthew DeCarlo]

Easiest likely solution would be to get your hands on an XP disc and run a repair installation.

 

[GNS1310]

Got the disk and the XP product key isnt working...I tried using the product key from my laptop, desktop and the one on the back of the cd case I have...none work. How canI get a working key?