log on problem

I have seen this happen under a couple of instances. One was when the time had expired for xp to be registered and it was not. The other was due to a problem device driver. For the latter, try booting into Safe Mode to see if you can get to the configuration screen and check for any devices which are not set up properly.

Cheers.

RW

Here's another possible cause (scroll halfway down the screen):

http://www.winxptutor.com/wsaremove.htm