ClamXav is a freeware virus checker for Mac OS X. ClamXav uses a slightly modified version of the tried, tested, and very popular clamav open source antivirus engine as a back-end.
Don it forget, if you run VirtualPC you can still become infected and lose valuable data on your Mac even though technically you are running Windows inside a sandbox. VPC will run any application you tell it to, virus or no virus, it doesn not know the difference.
