Can't Log on to XP

Everytime I start my Laptop, it brings up a blue screen as
if the computer had been left in standby mode. When I
click on the my user name to log in, it says "Logging
on..." and my Desktop comes up for a second, but then the
blue screen comes back again and it says "Logging off..."
under my user name, then "Saving your settings..." and
that's where it stays.

I've tried re-starting the computer in Safe Mode but still
get the same blue screen. I think it may have a virus.
Please help!