You can try Hewlet Packard, if they don't have them, I guess you're out of luck. It's possible if you can identify the maker of the components you could try them.
I belive that model is about 5 years old, so don't hold out a lot of hope.
A message to every one who is suffering sound driver problems in hp dc7600 ultra slim desktop computer, first you have to install windows xp service pack 2 and install all drivers , than install the patch file of service pack 3, than your hp dc 7600 auto update your sound driver,