We have an annoying situation with our nearly new Evesham pc where the system sound is completely muted every so often (at seemingly random intervals) on start-up. We have to do a System Restore to get it back.
There is nothing showing up as the cause of the problem when looking under Device Manager or audio troubleshooting.
Under Device Manager there are the following entries:
Sound video and game controllers
Audio codecs Creative SB X-FI Legacy Audio Drivers Legacy Video Capture Devices Media Control Devices Unimodem Half-Duplex Audio Devices Video Codecs
Creative is the default audio device and use only default device is ticked.
Sounds like it could be a corruption in the soundcard files/drivers. Have you tried to reinstall the drivers for them off the disk that you should have got with your PC. I have an Evesham PC and I got a disk with it which is called SUPPORT DRIVER CD, put this disk in the drive and it should auto run, then click on "DRIVER CONTENTS" then "AUDIO DRIVERS", then select the appropriate one for your sound card and see if this solves your preoblem.