Hi KLF!
It may not be worth upgrading a Pentium 3 computer, because you will still need new ram (DDR2) and maybe a new power supply (with ATX 12v connectors). Basically you would only be keeping the case, and the case is cheap — you might as well buy new stuff. New stuff isn’t expensive at all nowadays, I just built a machine today for 3200 SEK (315 euros) and that includes 25% sales tax!
This price included case, gigabyte socket 775 motherboard, 1gb PC800 ram, Pentium Dual Core E5300, a 4gb usb stick, AND an ESI Juli@ card!
These were retail prices (I bought in stores) — online would be cheaper.
///Leif