128 mb of ram wouldnt necessarily do that to xp. If there are severe problems other than being really slow, its not the amount of ram then. My brother (who i have urged to get some more ram) is running xp on a 1.4 ghz athlon with 128 mb of ram. Its like a turtle is reading the individual bits, but it still works and can open more than one window. Perhaps the ram sticks are faulty? If you have a custom built computer, thats quite possible. try downloading memtest86=> http://www.memtest86.com/ and running a few of the tests. Nothing else i can think of now that my mind is focused on ram lol.
Hope that helps.
Hope that helps.