You fear that evil unknown subjects might steal valuable information from your hard disc, while you are just trying to get some coffee? Then the Wireless PC Lock might help:
A Receiver is inserted into the USB port of your PC. It sends a signal to a transmitter your are carrying with you. As soon as you leave a radius of about 2m around your best piece, all accesses are denied. On your return it is unlocked automatically, of course.
The Wireless PC Lock supports Windows 98SE/ME/2000/XP and you can find a driver for Linux
here.