I am working on cleaning up a site that has a lot of infections. Sometimes the patient has a number of trojans and viruses in them that actively work to stop you from installing Kaspersky (and I presume Norton although I haven't used that.) It makes it a bitch to install KAV with many reboots and research on google and it always seems to change.

Is it possible/recommended to avoid all this by taking the hard drive out of the system, mount it on a clean system with KAV installed through a USB dongle (cheap -- less than $15) then telling KAV on the clean system to scan the USB drive? Is there some type of threat this would not catch?

It sure would save a lot of time; then put the drive back in the original system, install KAV there, and you're done.

Try creating a bootable rescue cd using KIS 2009 (PartPE, XP SP2). Then boot from this CD and clean the infected PC. I think it's a lot easier than switching the HDD between different PCs.