Have a friend who had their older computer infected with CBT-Locker; they took it to a tech who did not properly clean the disk before doing an install of Win7 over XP; and it persisted, apparently. Anyway…aside from cleaning up the mess, what was most interesting is that neither Avast (Free) or SpyBot S&D (Free) on this person’s machine detected it, despite boot-time scans.
Hope that’s not an indicator of things to come… 8)