If ClamAV seems like too much of a hassle, consider using one or more of these other portable malware scanners.

: You shouldn't keep this one--the portable version of one of the best free on-demand scanners--on your flash drive. Why? The dictionary is built into the file, so fresh versions come out every day or two. Download it from a safe computer at the last possible moment, and save it to your flash drive. Boot your friend's PC into Windows' Safe Mode, and run it from there.

: Actually, this isn't a scanner, but a portable, Windows-based analysis tool. It produces an obtuse report on the PC's configuration, and that report may contain clues about an infection. Consult for a list of online forums where you can upload your report and get advice.

: If you can't (or won't) run a malware scan in Windows, here's another live Linux distro built especially for antivirus work. You can download separate versions to burn to CD or to put on a flash drive. Either one is bootable.