I'm having the same basic problem. I too have the RealTek on board sound, but instead I get no sound at all. I've checked and rechecked my audio cords from the dvd burner to the motherboard, I've tried both cords, updated the firmwear, everything I could think of.
Here's some information that may help out:
Windows installed it as: ATAPI DVD DD 2x16x4x16
Region set to 1 (USA)
Tried to play using Windows Media Player 10
There weren't any drivers on the CD included with the OEM I bought from NewEgg, only programs.