xp pro profile size

I have 5 year old xp’s. Their admin profile including default user average around 1.5 mb unless someone puts something big on the desktop. I have 3 new xps with sp1 aready on them. The admin and default user profiles are all 32 mb on all 3 machines. If many users log in, I feel that the 32 mb is a bit hefty. What have I done to get such a large profile and is there any way to downsize it. I feel that this big profile is slowing down the unit. Because the default is also huge I can’t figure out how to make it smaller. I read that there is a registry hive that will restore a default user but I don’t know how to do that.