I found an answer to this problem
After installing Windows7 + Bootcamp drivers, you need to do a "special compatibility" installation of the sound drivers. So, after bootcamp has been installed, so the following
1.- Insert your original Mac OS install CD (the one that came with your MAC)
2.- Open the folder Bootcamp/Drivers
3.- Find the audio driver (Realtek or other) and RIGHT click on it -do not run it yet
4.- Select "Troubleshoot Compatibility"
5.- Let the wizard run. Choose the option "Troubleshoot program"
6.- Select "program ran well in previous version of windows"
7.- Click "test program" when prompted
8.- If asked to restart, do not restart yet -remember, at this point, Windows is just testing the program, so it hasn't installed yet. If you get a "restart" request at this stage it just means the program is actually ok for compatibility
9.- Back in the wizard, click "next"
10.- Wait for the drivers to install, and restart
11.- Enjoy HD music and mic!!!!!