Strange Windows volume issue

[cheaptonersucks]

Hi, we have a strange issue where if a student or member of staff lowers the volume slider in Windows 7 to it lowest level, when the next user logs in they cannot increase the volume, as the volume slider isn't visible!! The only way to resolve the issue is to login with the admin account and increase the volume, then log off. The OS is Windows 7 x64 professional. Just wondered if anyone has seen this strange issue and what the fix is please?

 

Thanks