vista is reali **** with ram. it has leaks all over the place with the main one being Windows Side Bar. my advice is to disable it completely. it isnt worth the hassle and aero takes up too many sytem resources to make it work nice and smooth.
p.s. generally talkin about OS's stick with XP SP3 RC1. the most stable and bugless OS. Vista is jus too memory hungry and compatiblitiy is better on XP
BTW: Aero (DWM.exe) & Sidebar are not the same thing... and both explorer and iexplore, even FF, are more "memory hungry" than Aero.