[Yishai]

I would like to shade some light on the subject
Windows XP 32bit can take advantage of 2.75gig ram by default Windows Vista 32bit recognize 3326 MB around 3.25gig
After Effect will perform much better Under Vista 32bit with 4gig of RAM it will allow AE to use 2gig of RAM (just for AE) and the operating system and other open Program utilize the reminder
Further more if you enable in the preferences Multiprocessing and YOU HAVE additional processor AE will take advantage of more than 2gig of RAM while rendering (it is actually running 2 copies of AE simultaneously.
And under Vista 64bit with Quad-Core Intel