windows 7 crackling sound


im fairly sure this will have been covered before so if someone could point me to the thread that would be great.

recently upgraded to Win 7 64 bit and when using Digitech RP500 aa sound card with Artist 6 i get the most horrendous crackling sound when the computer does anything at all. all drivers up to date.

system is AMD dual core with 4gb ram

onboard sound is working fine but is completely useless for anything more taxing than youtube videos

any help would be appreciated



ps have disabled audio enhancements already, no difference