Hey, I've been asked to help someone with their PC. It seems to have a Trojan and is running terribly slow. The computer is long overdue for a re-installation anyhow, so I figured I'd backup, wipe the disk, and reinstall XP. I just remembered that their Dell's internal disk drive is busted and they have an external USB drive, instead. Can I still install Windows from this external drive? How would I go about it? Do I need to set it as the default optical drive? Thanks!