Depending on your os and s/card the settings will vary , but I find that in XP and my XFi Music that things work better with the mic "muted" in windows for best results in BF2 . However , again depending on your hardware etc , sometimes you must UN-mute the mic in windows .
Try it both ways , as one of the settings should work .
And ..refering to the usb mic's ... I find that most usb mic's have a terrible time even being found/recognized in games . It just seems to be the nature of usb mic's in that requard . Direct sound card/mic connections are always your best bet for gaming .