http://www.pandasoftware.com/activescan/

Here's a place on the web where you can see if you have a virus. It takes some time to run, but works.

Some viruses will block Norton, if allowed to run. The email message that has the subject "Remove KLEZ Virus" is in fact an installer for the virus, and if you run it, it starts the virus and blocks Norton from ever seeing it again.

There are some harmless files that will trigger a virus alert. Old .com files from the days of DOS will bring an alert.

http://www.pandasoftware.com/activescan/