Check your sound card is properly installed, the drivers are properly installed and after that check your Sound control panel to see if it's all working, volume is up and Windows knows you want to use the sound card as the primary audio device.
Have you checked in the Asus site that Windows 7 drivers exist?
Where can i find for the drivers exist? actually, my just upgraded my OS. we don't have any cd's. Windows 7 did all the updates for my pc. I know nothing about this. please do help me. Does my motherboard have any problem with windows 7? Are they compatible? My motherboard is P5vd2-mx. Please tell me.. Thanks so much!