With that slow of a computer, i would personally go with 2000, but you didnt mention that so the next step down would be 98se, but security will be in issue and future driver updates. You may also want to think about any of the "light" versions. By using the light version of an operating system you will lose some minor fuctionality (everything can be done different ways), but you will gain a large proformance increase. And the last time i checked the lite installers were free. (you do however need a copy of the os you are trying to install).
Supporting AMD with your breakable stuff.