Been down that road already.
The stock drivers on disk suck. They wouldn't even load properly, and the tuner didn't work, and the capture software is junk.
I went through the BTWincap drivers installation twice, and finally got it right the second time, by using the installation guide (if all else fails, RTFM!)
Now every application I've tried captures and tunes properly, and I've narrowed it down to vdub for capping avi's, and an assortment of Mainconcept EVE, Intervideo WinDVR, and Sony Vegas 4 for capping mpeg-2.
Just this nagging little thing in vdub.
It's not a huge deal, I'd just like to know why it doesn't work?