you can't use DDR with older motherboards...or older (current) processors...
you need DDR RAM on DDR Compatible mobo with a DDR compatible processor
DDR Ram is out... technically... on the paper... good luck getting it though!
DDR mobos were out - they were recalled then. Waiting list (last time I heard) was months for pre-orders...
so, I wouldn't count on me being able to get any before February 2001, and stable, proven solutions until much later...
but, if you have networking or know where to look, you may be able to get them much sooner -- many people have them running already -- just not ordinary mortals like me