Your machine will not be able to run Vista so XP is your only choice if you want to get up to date with the rest of the world.
If you don't your machine will be stuck with 10 year old software that many new programs will not run on. Besides it's a small price to pay for not having to buy a new PC.
Windows 95 users are more than likely out of luck as most of the computers made in that time frame will not be able to run XP.
Edited by turn 5, 27 January 2008 - 02:33 AM.