|It sounds much more like address spoofing to me than a virus on the OP's computer. A virus on someone else's PC is the more likely answer. They have your email address in their address book and the virus is picking names at random from their address book to use as the "From:" address. That way the person with the virus doesn't ever know that their computer is sending these emails (any replies, complaints, error messages go to the innocent party).|
It's a very common technique used by virus writers.