I know Howard will be taking you through HijackThis. But I have a couple of questions.:
1. Why do you think you have viruses on your system> What's happening?
2. Do you have a current anti-virus program that you scan with regularly, updating right before each scan?
3. Do you have at least two spyware/adware programs that you scan with regularly, updating each right before you scan?
4. Do you know that an anti-virus program won't remove spyware/adware?
5. Do you know that spyware/adware programs don't remove viruses, Trojans and Worms.
6. Do you know that any malware infections, whether virus or spyware can stop you system from performing- well or at all/
7. Do you know that legitimate security programs don't pop-up and tell you that the system is infected with a large number of things, but you need to buy their program to get it clean?
Keep those things in mind for when you get lean-so you'll stay that way.