This can probably only be done if you had third-party software in place already, like Norton GoBack or Ghost. As a preventative measure in the future, I recommend getting Norton SystemWorks Premier which includes GoBack, Ghost and Antivirus. You should first try to fix the volume by using the "advanced" volume tool. Start, Run, sndvol32. This tool will give you a lot more volume sliders to fiddle with. Windows does have a built-in System Restore function but I believe it only fixes driver problems. If sndvol32 didn't work then your volume problem may be driver-related so you may want to look into System Restore. Go to Control Panel, System, Device Manager, find your sound card, Driver, Roll Back Driver. I think this has about a 20% chance of working.