You're going to have to free up some space to install antivirus software. Easiest thing to do about software is go to either www.symantec.com
and look for the trial version of their AV software. The Norton AV (by symantec) is about a 27Mb download... I don't know how big McAfee is though. The actual effects depends on exactly which virus you have. Download and run the AV software, then check the virus database of the site you downloaded from to see about anything else you might need to do to clean up from the infestation.
BTW, moving to Computer forum...