Thanks for the vote of confidence, Claire.
You definitely should not have gotten a virus from here, free_sprtd. You mentioned you got a virus a week ago from limewire. Do you know the name of the virus you had? If you tell me I can find out more about it for you.
I'll bet it's the same one rearing its ugly head again. Sometimes these things embed themselves very deep into your operating system. When you say your boyfriend wiped the pc, did he format the entire hard drive to remove every last file and reinstall windows? If not, it's possible that the virus was still there - dormant and waiting.
There was recently a virus that exploited a vulnerability in Internet Explorer that swept the entire Internet. Do you use Internet Explorer? Have you installed any patches or anything Microsoft may have released to deal with the issue? Your operating system may have downloaded and applied any necessary patches automatically. I would look into it, though.
I would definitely install at least a free antivirus program like the one Claire suggested, though I haven't tried that one personally.