Combofix disables autorun to help with these infections, meaning if
you plug a usb stick/cd's in they wont automaticly open.
Having said that im not seeing the infection yet.
Is nav still seeing infrom.exe ?
If so id like a copy, you might have to temporaraly disable nav
submit it here please
http://www.bleepingcomputer.com/submit-malware.php?
also submit autorun.inf if it is present in same location as infrom