SN25P - microphone is extremely noisy

Hi,

Just build a system with a SN25P, 4000+, 7900GT, and it's really
working quite well.

However, apart from the sound playback being a lot more "tinny" than
the Audigy2 ZS in my old system, I pretty much can't use a microphone
at all! It's very noisy, with a pulsing sound, outdrowning whatever I
say.

I read that the drivers on the cd can cause problems (though noone
mentioned the problem I'm having), so I uninstalled, ran drivercleaner
pro, and installed the newer driver from via's homepage. Still the
same problem.

Does anyone have any experience with this problem?

I'm considering putting a FW/USB sound-"card" on the box instead, but
surely that shouldn't be necessary?
--
Lars Balker Rasmussen