hi gully, if you havent done any reformat to factory defaults on your computer, i suggest trying this option
(i came up with this idea just last night when i encountered a computer with a curious problem)
Click the Windows Start button
Select Normal Startup
Restart your computer.
i thought we should give this a try. this basically tells windows to load ALL drivers and windows services. The possibility of the Windows Sound and Installer service is unlikely with normal use, it can still be disabled at times.