If you are on a network, pull the cable so as not to infect anyone else.
Remove all of the programs and reboot.
Re-install one of them.
I prefer Avast 4
www.avast.com it is free for home use, and works well.
If you think you are infected, do your scans in safe mode.
I think I have a virus on my computer. I have a McAffee anti-virus program and a Norton anti-virus program. However, whenever I start scanning the computer for viruses using McAffee, after about 10 seconds the program shuts itself down. Same with Norton. Frustrated, I then downloaded a free trial version of F-Prot anti-virus and a free trial of AntiVirus & Trojan. Both programs do the same thing when I start them up: after about 5-10 seconds of running they just disapear. Any suggestions?