Audio card going?
Computer is a 1 year old HP media center.
New video card is EVGA Nvidia GTX 275, OCZ power and cooling 750 psu.
No problems before the swap.
Did you uninstall the old Vid driver before uninstalling the old card?
Did you make sure that the onboard vid was correctly shut off in the Bios?
Go to the Vid card manufacturers website for the latest driver?
Uninstall the soundcard driver, and install new driver from the chipset manufacturer?
Never go to the MS website or the HP website to fetch the standard drivers from the assembler.
I use HP MediaCenters when I don't scratch build.
Thats what works for me, and YMMV.