Dont listen to KOMMANDER.
Ventrilo has always worked in Windows Vista, even when Vista was still in beta.
Even Flagship (The developer of ventrilo) said this about Windows Vista in June of 2006:
I finally managed to get Vista installed on my test machine. Never seen an OS be picky about the the drive type.
Anyway, after getting all drivers setup and the system stabalized I was able to get ventrilo up and running with 0 problems. I just now started a continuous stream and will let it run for a while. But it looks like it works fine for me.
The only widespread problem people had when Vista was still in beta was the PTT not always working. Even still, there was a work around for it.
Now what causes the "HR=DSERR_NODRIVER" error...
1) Make sure that your headphones and mic are completely plugged in & that they are in the correct ports. Windows vista and certain sound cards (including onboard) are able to detect the headphones / mic being unplugged and it will result in that error.
2) Make sure that you have the latest drivers for your sound card and that the software is installed and running. There is normally a program that starts with windows for the sound that comes with the drivers. Do not delete it from the startup.
3) Make sure you are running the latest version of DirectX
Those are the main things that i have found fix that specific error.