Well I still had problems of rebooting when it felt like it in SH3 and whilst running Jet Audio on the internet.
I finally disabled AC97 Sound in the bios & installed an old PCI sound card (Creative CT4730), now everthing seems to be running great!!
I have now ordered a Creative Audigy 4 sound card & hopefully all will run. (my wallet only has moths now!
)
Seems a shame to throw the onboard sound away & I have tried installing the lates Codecs from Realtek, Beta version of drivers at Asus but all attempts to fix the problem failed!
It's amazing how others with the same board & video card have had the same problems but their fixes didn't work on mine!! such as disabling fast writes, setting AGP to x4 etc, who knows!
Cheers