I had a P233 for ages, but the mobo died when I added new memory. Incidentally, a lesson from that - when installing new memory, always take the mobo out and do the job on a flat surface. If you try to do it with the mobo in the case, you'll bend the mobo pushing the DIMMs in, and that may kill it.My new one's self-built anyway, 3 months back - cost £200 for a mobo, Duron, modem and new case. Definitely the best way - you don't need a new hard drive, a new monitor or new memory unless you're going for a real spec upgrade. It's nice to have, but you don't need more than that for office-type stuff, so everything else (CD-RW, hard drive, memory, graphics card) I just stripped off my old machine. Took a few goes to get everything working, but it went in the end, and it would have cost _significantly_ more than £200 for a new machine.
Plus I wouldn't have got to choose the spec I wanted. An ISA slot on the mobo was essential to let me keep my old parallel port cards - PCI parallel port cards cost a fortune. And lots of PCI slots on the mobo too for expansion. A proper modem (not a WinModem) is essential too.
An AMD processor is the only sensible choice. If you think there's the remotest chance you'll want to upgrade, do not ever buy an Intel. AMD have one processor socket, and everything backwards for some distance and forward for some time too will fit that socket. Intel have invented a half-dozen different fittings, so if the processor or mobo goes then the chances are you won't be able to find anything to match it, or you won't have any choice in the one or two available. A good idea it is not, young Jedi...
Graham.