I am using Windows 7 RC Build 7100 on my desktop, mainboard is Asus P5GC-MX, chipset is 945GC, sound card is Realtek HD Audio. I installed their drivers successfully. Source http://www.realtek.com.tw/downloads/downloadsView.aspx?Langid=1&PNid=24&PFid=24&Level=4&Conn=3&DownTypeID=3&GetDown=false Direct X 11, too, although I don't see tab music? Windows Media 12 plays music normally But I can't hear anything from my speaker, although i turn the volume control of Windows and the speaker to maximum, and i don't mute anything. When I start this PC with Windows XP, it work well, I can hear the sound normally. So my hardware is good, maybe the result come from the software (driver, windows 7 rc, ...). Why this problem appears and how to fix it? Thanks for reading my post.