Event Sounds Problem

Very Strange and Annoying! For some reason just befor an event sound plays I get a crackling sound that usually cuts off the begining of the .wav sound file. Every test / diagnostic says that nothing is wrong but this is not right. The only test that indicates something is wrong is the Yahoo Messenger Audio test. When it runs it sounds like a thumping heart beat and completely locks up my computer in the FEEDBACK test. Any Ideas on how to correct this???

 

Maybe checking for an updated audio driver.

 

Thanks for the tip, it's one of the 1st things I did.
I've gone through all drivers and checked for up dates. Installing what's new but the problem continues.