Screeming in the Big Freeze

[Fourx]

Here goe's

I have the following spec.

K7VZA mainboard with Thunderbird 1.2 ghz processor (i think)

Machine works fine with onboard sound but has poor sound reproduction.

I have two cards for sound - SB Live and SB audigy. If I fit either of the cards, after about 10 minutes the sound lets out a loud screech and then freezes up.

I have tried everything I know to fix it but problem persists.

I have gone back to using onboard sound

Can anyone help?