FYI, Macs can get viruses just as easily as PCs. There's a Mac Trojan in the iWork 2009 torrent, from what I hear.
If you own a Windows PC, it's just as good as a Mac. Get an anti-virus program, and run scans with all of them. Leave your computer for about 30-45 minutes, and then go back. The scans should be complete, and then you can tell the programs to delete the viruses. Job done.
I'd recommend getting ThreatFire, HijackThis and AVG 8.5 Free.
ThreatFire
AVG Free 8.5
I can't find the download link for HijackThis, but look on Download.Com. It's free as well. Once you've got all that done, make sure to download TuneUp Utilities 2009. There might be traces of the viruses still on your hard drive. Get TuneUp to fix the registry and defrag the disks. TuneUp isn't free. Just download the trial. It lasts 30 days, and then you decide what to do after that. Buy it or uninstall it. Don't matter.