All microphones output only static

My laptop has two built-in microphones and I have a USB sound card with two microphones built into it. Both recording devices show up in software but if I try to use either of them they output high pitched static for a few seconds and then go completely silent. The right channel always cuts out first. If I click on the "Recording" tab in the Sound dialog CPU usage maxes out and the box freezes until I kill it with the task manager.

I have a Fujitsu Lifebook T4210. T2500 2.0 GHz Core Duo, 2 GB RAM, SigmaTel Audio (using latest vista drivers, no 7 drivers available). The USB sound adapter is a Turtle Beach Audio Advantage SRM.

Thanks for any help.

Edit: Also, everything works right if I boot into XP, so it's not the hardware.

I'm wondering if you have the codec installed also try [SigmaTel High Definition Audio CODEC 6.10.0.5609

I have Sigmatel V6.10.5866.0, which would appear to be a newer version.

And that wouldn't explain the USB card not working anyway.

Edit: Tried to install that driver anyway. Get an error after unzipping.

Do you happen to know the manufacturer and date of the driver for the Turtle Beach Audio Advantage SRM?

I'm asking about the manufacturer to see if it's using a generic Microsoft driver.