I have a Tascam US2000 and could not for the life of me get it to show more than two channels on my Windows 7 machines. It worked fine on my Apple stuff. I do IT work and couldn’t believe that the rumor that Macs were better was true (I think its all marketing like the old days of Ford vs. Chevy). After a little digging around I found the interface host setting of Windows WDM-KS did the trick. Audacity (the best free software in the world) works great on my PC now with the US 2000. I’m willing to bet that a few people with other “streaming” interfaces that can’t see more than 2 channels have the same issue. I hope this helps someone. By the way as for the Apple VS PC, Ford VS Chevy thing… Its time for Teslas! 
Thanks, unfortunately the upcoming 2.0.5 release of Audacity no longer includes WDM-KS because it has caused stability problems on a small minority of machines. We hope to reintroduce WDM-KS in a later version of Audacity.
Gale
I’ll have to stick to version 2.0.4 myself. WDM-KS works perfectly well on my system to record streaming audio from browser or from Line-in input. On the other hand, I could never make MME or DirectSound work satisfactorily. WASAPI does work, but it is restricted to 44Hz, which is too low for my own taste.
I do hope that WDM-KS will be reintroduced quickly.
Robert
The problem is almost certainly in PortAudio.
We can probably fix the scenario where Audacity never starts due to WDM-KS, but the difficulty is in fixing the blue screens, unless we (or the PortAudio developers) can get access to a machine that does it.
It’s possible to allow the user to enable WDM-KS with a warning. It may be all we can do.
Gale