Sorry to hear it, The4thnobleman. Griffin's advice is your best bet. Of course if they keep using the machine without wiping it, you can snap up all kinds of information. I think the first thing I'd do if I got access to my stolen computer would be to install a keylogger (e.g. pykeylogger.sourceforge.net). There's probably more specialized software for this out there too.

Keep your spirits up and take good care of your parents! Remember that the pitiful opportunistic burglar is probably a poor, drug addicted, wretchedly unhappy fool, whose miserable existence is likely already beyond the punishment you'd wish for most thieves. (Not sure what my point is, I just find that this mindset appeases my lust for vengeance somewhat).

This got me thinking about DIY theft/recovery thingies for desktops. One could probably make a pretty devious one with the Raspberry Pi and a GPS dongle, inconspicuously mounted in the case. Perhaps GSM dongle too. Hmmz. Actually, a cheap phone, duct-taped somewhere clever would maybe work too. It'd get power from the desktop itself (or in the case of a phone, be charged). Ideally, it would be able to monitor the desktop machine's activity, at least log keystrokes.

Now that I think about it, just having USB GPS & GSM dongles attached at all times (ideally mounted hidden internally in the case, but obviously with reception) would kick ass. The software would be lost when they wipe the disk of course, but I bet in the majority of cases, the box is booted at least once. *heads off to dealextreme*