I agree that linux is far from the best OS on desktop. I certainly believe it is better than windows though, much faster on my system atleast, even my k6 450.
Remember to not install unecesarry services and programs that you will not use, removing those will highly increases both boot speed and memory.
I kinda like debian, even fast on older hw, but is a bit more complicated than mandrake and such.
You could also try knoppix, which is a live-cd distro based on debian, but includes a install script :-)