Let me suggest you apply windows updates if you don't already do so automatically. And maybe do a manual update just to be sure.
There's a particularly nasty security hole that Microsoft provided a patch for this Monday. It's a big security hole and there are computer criminals out there trying to attack machines that aren't patched.
If you have Windows XP, you must have SP3 applied, or they patch is not available.
Microsoft has abandoned anyone still using Windows 2000 or NT, and will not be publishing a patch for you despite the secure security hole in their defective software.