Yeah I think that rules out sound, and there haven't been a lot of posts about catalyst drivers causing trouble so it's doubtful it's them.

if prim95 passes your cpu is probably fine, OCCT is also a good system stresser, it tests GPU now though I haven't used that much as it's new and I haven't been playing with overclocking.

There's also Furmark and ATITool for stressing graphics cards.