How do you know you have a virus? What's happening?
You can get some free scanners to try and deal with it and see if it works. If it's spyware related, try using AdAware, it's a free download. Give it a scan, see what comes up. Also make sure you have a firewall. ZoneAlarm is a phenomenal firewall, and it's free. It is actually rated better than most firewalls that cost $70 in stores. Get ZA, scan your comp and keep ZA running at all times in the future.
If that doesn't work there is a program called search and destroy that will show absolutely every process that your comp is running. You would need to run that program and then paste the process list either here or on a comp site so that someone can look at it and see if you have any malware or anything that the firewall and spyware scanners didn't pick up.
If none of those options work, then your only real options are its either A) a computer hardware problem and the store needs to fix it, or B) Reformat your computer.
i had a new years party and had my laptop hooked up to the stereo in my basement and people were picking music all night, i wake up the next day and my 4 month old laptop is plastered with spyware, same pop ups you were getting, i was furious, but all i did was a system restore to a week before and it fixed everything, so try that. start > programs> acessories >system tools
f you do the sickest switch cork ever people will still say why dont you have bigger pants" - Fr2planker