Congratulations, you're the latest to experience Creative's wonderful "squeal of death".
From a news item released in 2002:
Creative Technology Ltd.'s latest Audigy sound cards seem to be plagued by an elusive "squeal of death" that is causing random lockups in PCs using the card and the latest Windows operating systems.
The error was reproduced Friday at the company's Singapore headquarters, as well as at Creative's testing and support facility in the U.S. So far, Creative has neither identified a cause for the glitch nor a single unified solution to work around the problem.
Unfortunately, this problem has never been solved, and affects every card in the Audigy lineup, including the Audigy 2 ZS. There's a thread on the Creative forums that, at least glance, was almost 30 pages long, filled with a myriad of complaints about the exact same problem you're experiencing.