Windows 7: No sound in windows 7 after BSOD, tested with 3 different soundcards

*EDIT* I cannot seem to delete this. i have posted it in Sound instead - despite it probably being a driver issue.



After an update last night (but not SP1 - this is now installing) there was a BSOD on bootup and then no sound at all. I have an external card (Fast Track) for recording, an internal card for watching movies (x-Fi titanium) and the onboard which i have disabled. None of these are picked up by Windows 7 - the audio in the taskbar says "No Audio Output Device Available." They appear in Device Manager, but with a little yellow ! sign by them, and it says driver installed but "Code 39." This is definately a Windows error - I plugged the fasttrack into a mac and it worked fine, so the soundcard is not burnt out.
I tried rolling back the drivers - this did nothing, and it only gave me one choice to roll back with. I have a deadline to export music by and its giving me a major headache.
Anyone have any idea why Windows would suddenly decide not to see sound cards?
i have tried reinstalling drivers, unplugging the internal and external soundcards, scanning for new hardware and nothing works.
Any help would be appreciated, Pete