I think my (somewhat) new computer has a virus, do I really have to pay Dell $129 to get rid of it?

I got a new Dell desktop 4 months ago. The past week or so it has been acting up. It won’t always connect to the internet, the pages load slowly and I get a lot of “timed out” messages. I called Dell because I have a couple of years of support that came with my purchase, but they said that it was a software problem and that wasn’t covered. They checked it out remotely with “HijackThis” and hinted that there is a virus and other problems that they would need to take care of. They want me to pay them $129 for a onetime fix.
Is this really what I need to do to get my computer fixed?
I think that the HijackThis left some kind of report on my computer, but I’m not sure.
Can anyone give me some help or advice with this?