no sound in user account

[powen]

The sound on a friends system has stopped working.
I checked the device manager and there were no conflicts with the sound devices.
I eventually found that the problem only occurred in one of user accounts.
If I logged in as administrator (through safe mode) all the sound worked fine.
In the user account, when any sound was played a message appears saying no sound device installed.
I have tried re-installing the AC97 adio drivers but it has made no difference.

system:-
win xp pro
Onboard sound card
1 user set up (did have admin wrights but since problem occured a new admin has been set up and the main user given limited access)

Any ideas as to why this is happening?
Thanks
Paul