Physically securing desktop lab computers

[Billfred]

Well, this is one that has me stumped.

I'm the de facto manager of my residence hall's always-open computer lab, and recently we've had a couple of parts walk off. A monitor disappeared last spring, but reappeared around finals. (They've since been locked down far better.) When I first checked out the computers this fall, a keyboard and an ethernet cable were missing. While I know these parts are cheap and available everywhere, it results in downtime for the computers (and, as with most state institutions of late, we're not made of money).

So, with neither the business manager nor myself happy with the situation, I've been looking for a means to keep folks from accessing the cables on the back of the case (thus keeping them from making off with the items), while still allowing folks to access the drives and USB ports in the front. All of the searching I've done hasn't turned up a system that can do both (either you could unplug cables, or you couldn't access drives). My inclination is to build a case over the case from plywood, leaving holes for ventilation and drive access, then perhaps paint it to make it look nice.

Has anyone found a solution to a similar situation?