|There are some pop ups out there that will tell people they are infected. If it is not from your own anti virus program the pop up should be regarded as a malicious file. |
Never go to their site and download the anti virus program the pop up is recommending.
I would try a "live cd" that has an antivirus program on it and give that a try.
It sound like your computer has a nasty file on it. It is possible that any computer you hook the hard drive up to that has a good antiviral program can scan and clean it up.