Disable Entertainment

Hi,

My friend is a doctor. He runs a small clinic which has three desktops running xp. He uses them for accounting and file reviews. Some of his employees have begun to use the PC for entertainment purposes - Movies/Music. He wants me to disable these features permanently on these systems. He needs installation privilege so that new updated software can be installed. I could only think of the following.

Disable Sound Card
Remove any kind of media player including WMP
I also thought of deleting codecs from control panel>sounds and audio devices>hardware>video codes>properties. Will it work?

Any brighter suggestions are welcome. Will the Administrator Rights prove any use in a situation like this?