I think you need to update you Virus software and run a full virus scan on
your PC. There are free scanners on the Internet, but can be quite time consuming.
I've always found it best to have the latest software and update it at least once a week.
Set your system to run a scan once a week after the update.
We scan nightly on every PC and the client PC's check for updates from our virus server
before the scan. We use Symantec which I believe actually only releases definitions on Friday.
E-mail if you need anything, glad to help.