Welcome to the forums.

This sounds like adware/browser hijack, not a virus per se.

Try Adaware se and Spybot first

http://www.lavasoft.de/support/download/

http://www.safer-networking.org/en/index.html

Post back with the results and some more information about your system so we can help you further. O.S. (Windows version 98 m.e. xp nt etc.)

Also a Hijackthis log would be useful.