I removed the center drawer and mounted a keyboard slide where the drawer once was. To make it fit required that I cut the keyboard slide in half. make it about a half-inch narrower, and splice it back together (using wood underneath as a reinforcement).
Next I gutted the two bottom drawers on the right-hand side and used the old drawer fronts to make a hinged door. This is where the computer goes. I also cut some vent holes in the bottom of this area and in the back for ventilation.
In the top drawer on the right-hand side I installed a panel to hold a mouse pad. When not in use, the mouse stores at the back of this drawer and the drawer can be closed.
This makes for a pretty compact computer desk, and when the keyboard is retracted and the mouse drawer is closed, it doesn't blatantly scream "computer desk" at you! Overall, if you're reasonably handy with woodworking it is not a difficult project.








































My keyboard drawer was like yours, and it's a large piece of plastic with metal slider rails and bearings attached to it. I completely did away with the plastic shelf and cut a piece of plywood to fit the keyboard, and mounted the rails to that plywood shelf. If you do this, I'll bet you can at least use a portion of the center drawer front (cut down so it's as wide as it was before, and just a few centimeters high) and fasten it to the keyboard slider wood, for a very nice look.
Second, I imagine the bay on the right with the hinged front is for the CPU. If so, I'd cut out the back of it completely (or at least drill a lot of holes) so that the CPU gets enough air for cooling. My old P4 system would bake itself in an enclosed space like that (although, I bet it would be a lot quieter!). I did this for my entertainment center I built - all the ones I saw in the store were pretty much closed in the back, and I really didn't see how that was good for the circuits).
Cheers!
If I had it to do over again, I think I would have replaced the plastic slider with plywood as you did. It would have been much easier to adjust the width of a piece of plywood than the plastic keyboard holder. Thanks for your comments!
By the way that's not an old desk, it WAS an antique - a rather nice one, at that...