I've recently encountere this problem (didnt have it before):
Whenever I'm using fullscreen mode - in PR, BF2 vanilla or any other game - I can hear random annoying cracks that could be compared to intense radio disruptions.
What is more, youtube videos when fullscreened have the same audio problems with video leap-frogging. Checked on other sites - same (even southparkstudios.com dont work
Also, no problems with Divx movies, Pacific episodes etc. even in fullscreen mode.
My specs:
CPU: Intel Core2Duo E8200
GFX: Nvidia Geforce 8800 GT 256 mb
4 GB RAM
Sound card: Analog Devices SoundMAX Integrated Digital HD Audio
OS: Windows 7 Pro 64-bit (legal with all the updates)
Halp!

