It's a Release Candidate (RC) SP3 for WinXP... not a final build!
Haven't found an official Gigabyte forum. And there's nothing about PCI Express X-Fi cards yet...
Creative tech support replied I should try the card in another PC, which is not possible at the moment as I don't have a spare PC with PCI Express slot. Otherwise I should send the card for RMA. It's interesting, though, that I heard some really nasty pops on X-Fi while playing a typewriter sound repeatedly. When I did that thru the Realtek onboard audio I didn't hear any sound distortion!
Hmm, perhaps it would be worth to try a setup without PCI Express graphics. I have an old Matrox Mystique 4 MB PCI graphic card, which should work fine for some basic tests in WinXP. That way I could make sure whether ATI Radeon HD 3850 causes any excessive EMI...