i went from a 2800+ t bred m8, and i wasent expecting to see any real improvment in everyday things. a higher end xp is still no slouch on the desktop. certainly, if your talking about windows boot up times you need to take some factors into consideration:
have u changed your hdd's. there the biggest bottleneck of all in any system, spesh for stuff like loading windows!
have u had to tinker with your ram: did u only have pc2700 before? are you still using pc2700 now? did u have ddr 400 and beacuse you were running it at pc2700 you were running it with trick timings, and now you have it at 400 youve had to knock them down?
have u reinstalled you windows install???
to be honest i imagine the memory question to probably not have much impact on the situation anyway, due to the nature of the a64s on die controller, its not like running slower ram than your system bus, the oenaltys not as bad. if it was to be anythig i would say about the hdds or the windows install on there from the previouse setup slowing you down.
that said you might just not notice anything intill you strech her legs so to speak. sit down and play some games, maybe encode a div-x. theres where you will see your diffrence
Or for ultimate gratification, install the beta xp pro x64 edition
karlos