that are infected. Have you got a name for it yet through your scans. Have you ran HiJackThis yet. If you have post the log file. It could be prnjobt.vbe VBS/AutoRun-IT is a script worm that spreads via removable drives. Don't use your USB sticks or drives as we will come to that later. Concentrate on the workstations first.
http://www.sophos.com/security/analyses/viruses-and-spyware/vbsautorunit.html
From another PC download and install these two programs and copy the the installed folders to a clean USB Stick or burn them to a rewriteable CD.
Restart the PC in Safe Mode and turn off System Restore, then run Sophos and then run Spybot.
Download Spybot - Search & Destroy and install it. Update it. http://www.safer-networking.org/en/download/index.html
Download Sophos and the latest IDE Files. Install it and extract the IDE files to the C:\SAV32CLI folder.
http://www.sophos.com/support/knowledgebase/article/13251.html
Copy and paste the below two lines into Notepad and save the file to the USB Stick as sophos.bat, it will scan and remove. When the Scan has finished check the log file to see what it hasn't removed.
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CD SAV32CLI
SAV32CLI -REMOVE -P=C:\REMOVLOG.TXT
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The Sophos SAV32CLI folder can be safely deleted after it is copied to USB.
Keep us informed as to your progress.