I have re installed OS many times(XP PRO) sound was working.
Last time I have Windows 7 Ultimate ,Sound was working.
I have formatted Windows7 (C drive only) and installed windows XP again,installed SP2 then SP3. Installed drivers.this time I don't have sound in my system.
Control Panel> Sounds and Audio Devices> shows No Audio Device .
Device Manager shows Yellow Mark on Sound driver "Realtek High Definition Audio".