I don't, because all I run on Windows is... uh... IE (for testing site designs only, I swear). oh, and
ARSENAL Extended Power, because it's old and primitive enough to run emulated. so if I get a virus mucking with one of my emulated PCs, I just delete the PC and reinstall. easy-peasy. personally I can't imagine relying on VPC for much more. if you're using it that much, build yourself a cheap one and use a KVM switch. saves you the indignity of seeing the "Welcome to Windblows XX" screen on a Mac. though, it also means you miss the wonderful moments like this:
Yohan, huh?