I'd set each of the six up as a slave, then connect one of them and scan it with anti-virus software from your from your C: drive. Once it's disinfected, repeat the process with each of the six in turn.
I shouldn't be too paranoid about infecting your C: drive. So long as it has an anti-virus product already installed, you should be fine.
Try installing TDSSKiller, and the free version of Malwarebytes' Anti-Malware and the free Kaspersky Virus Removal Tool onto your C: drive first, then connect an infected slave, and boot into Safe Mode with Networking before you perform a scan.
Try this:
Firstly, boot your computer to the Safe Mode menu screen. You do this by repeatedly pressing F8 as soon as you boot up. Once there, use the arrow keys to highlight Safe Mode with Networking. Continue to boot from there, by pressing Enter. You will now see some drivers being loaded. There will be a pause at some point. This usually lasts for no more than 30 seconds.
If that's successful, download and run TDSSKiller.exe from Kaspersky Lab. It's tiny, and takes just a minute to run. It hunts down and kills a specific family of rootkits:
http://support.kaspersky.com/viruses/solutions?qid=208280684
Regardless of the results, download the free version of Malwarebytes' Anti-Malware (MBAM). Install it, get updates and run a full scan (still in Safe Mode). This is a direct download link. Copy and paste it into your browser’s address bar, and press Enter.
http://www.myantispyware.com/mbam
After that, boot normally and run another full scan with MBAM. It will detect any malware that wasn’t running in Safe Mode.
If the problem still exists, download and run the free Kaspersky Virus Removal Tool:
http://support.kaspersky.com/viruses/utility
You should now delete TDSSKiller.exe and the Kaspersky Virus Removal Tool, as updated versions are often made available. Malwarebytes' Anti-Malware can be easily uninstalled, should you wish to do so, but it may prove to be beneficial in the future.
Hope this helps.