Virus software program to start, try AVG Free 7.5. Then boot your PC in 'safe' mode (hit F8 during startup) and run a complete virus scan on all drives.
This should remove all of the viruses and allow you to get back on the net.
Cautionary note - Make sure you have a firewall (windows is fine) and an anti virus solution before going onto less safe sites :)
Darren
April 2007