Sound can be disabled completely via the OS sound controls, however the Event Viewer logs would probably be more useful to look at. It'll show detailed error information including error codes. Also, check for running processes, there may be unintended things running ( i.e viruses, etc..). There are some things you can pick up that will attempt to run programs over a network connection ( whether your connected or not ) like audio or video files. There are various tools to use, Software Explorer in Defender ships with Vista and will do the job. An app called Process Explorer will give a more detailed view.This is a free download from Microsoft. Audio drivers should also be looked at. Vista had an early history of driver issues. I have been running Tacops for a year while on Vista without major problems.
Try the audio driver first, it's the easiest thing to do. I recently had a microphone problem with a new head set and the driver update fixed it immediatley. Sorry I didn't mention it first. Hope this helps. I hope you're happily blasting OPFOR soon!!
Best wishes, Sprocket62