hi, i recently upgraded my pc with a geforce 8600gt video card and everything was fine. my sound worked fine even when my computer restarted. however, after i shut my computer down and did a cold boot, my volume control says "no audio output device is installed", my device manager no longer shows my sigmatel hd audio driver, in the services menu the sigmatel audio service is stopped and when i try to start it, it says that it started and then stopped because "some services stop when they are not in use by other services or programs". the sigma tel audio icon in control panel tells me that the driver is inaccessable and i cannot reinstall the driver. i know this is pretty rambling but these are all the solutions i have tried already. i do know that if i uninstall the video card and restart my computer, my sound works and i can then re-install the card, but then it starts over with sound working until i shut down the computer. thanks for your help, if there is any other information that will help, please let me know!