If you look with allocation tools like fdisk, there's usually about 8 megs of unalocated space. That's where the infection would place its file system.

Kaspersky's tdsskiller utility is supposed to detect these infections and clean them up. Haven't tried that yet, because I got this one by another means. Only by doing so was I able to find out what to look for to fix it.

I ran Combofix in Safe Mode. It found root kit activity as usual and started its special reboot for clean-up (which doesn't work in this case). I killed the reboot, booted into Recovery Console and replaced the MBR using fixmbr (which runs only from the recovery console). I then rebooted into Safe Mode. The startup was intercepted by Combofix as usual but this time it detected TDS4 infection and killed it.

I don't know if fdisk would cure this problem - it might, but it might not. If I really wanted to be sure, I'd hook the drive to another system and use a disk editor to overwrite the whole MBR with $00.