This is part 2 of the computer cleaning recommendations I started earlier today. While I may agree this stuff isn't exactly cool or entertaining, neither is the frustration of a machine that won't function properly for you. Consider it the equivalent of changing you car's oil & checking the tires.
In this day & age of viruses, worms, trojans, adware and spyware, a periodic thorough virtual housecleaning is a survival necessity. One of the side benefits is the steps will likely make your computer faster & more reliable too.
The first thing is to be certain your antivirus definitions are up to date, (I recommend doing a forced manual update to start the cleanup process.) Run a full system scan with your antivirus program. Then, to be absolutley certain, it's a great idea to run a second scan using a trusted online virus scanner as well. Occasionally one company's product will catch something another missed. Here's Symantec's online scanner, and the online checker by Trend Micro. Use the one that's not from the same maker as your machine's antivirus program.
Once you've gone after the viruses, it's time to go after the other nasty beasties that may have invaded.