In Vista this can be done in several ways, but all involve 3 or more menu choices.
In the public domain there are a number of freeware programs for this, but all seem to have problems on Vista.
The most promising was Vista Audio Changer.
I installed this but was not able to make it work because I run a Dutch Vista and the algorithm used seems not to like this and I was not able to make it work under Vista NL. I reported this to the author but got no reaction.
After leaving the subject alone for a while I continued my search and stumbled upon
I little gadget for Vista that was easy customizable for Vista NL. The only problem I was struggling with for a while was the fact that according to the instructions I had to place the executable file in the system32 directory. The gadget worked but everytime the Vista security kicked in and asked for permission. I placed the file in a directory of its own c:\Audioswitch and changed the gadget code and now it works like a charm.
It must be noted that the Vista Audio Changer seems more feature rich especially that feature that you can switch based on an application is something you want. Hopefully I can try this out when I can make it work.