If you have the extra slots, then I'd say get two more 512mb dimms rather then buying 1gb dimms. The 512mb dimms will be cheaper.
Also 32bit Windows will only see 3.38gb, (approximate), anyways, so why buy memory you won't be able to use. If you're running windows 2000, I believe it will see the full 4gb, but not certain of that.
Wabbit
Morals & Manners Officer
Whitey's Buccaneers
5th Army Air Corps