windows audio service not enabled

I have recently lost sound on my Dell laptop. When I try to get sound the volume control option is greyed out and it says the windows audio service is not enabled. I have tried typing the command "net start audio srv" in run, but that didn't work. I have gone into control panel>administrative tools>services and tried to start windows audio, but it gives me the following error "1068: the dependency service or group failed to start", but i don't know what service or group it is referring to, so now I am stuck. :cry Vista os.

Please help
Thanks

 

Hi
MMCSS throws an error when I try to start it. It says "failed to read description error code 998".

I have reinstalled the audio drivers. All the device managers look fine (no yellow !). I don't know what the UAC is, so I don't think I have turned it off. The sound worked fine one day and not the next. I suppose there may have been an automatic update or it may not have been shut down properly (technically inept husband!)

Thanks