I finally got the CoD4 Multiplayer to run on Vista. I've tried pissibly every major solution on the web, & the microphone-related one was the only one that worked.

For those who are having problems with CoD4 MP & are using a Dell XPS 420, the microphone jack IS NOT indicated by a pink ring. It's located at the front of the computer, & is indicated by a tiny microphone symbol.

Time to kick some butt :D

Ash