Wait until you try Vista x64 - it takes up about 50% more RAM than the 32 bit version...

I've gotten Vista down to about 230MB average (nothing running) without forced deallocation (forcing everything onto the page file).  Still unreasonable for my purposes.
I have 1GB, but it's dual channel DDR500 (I prefer speed over capacity).  Hehe, my RAM setup is still faster than most DDR2 setups today :P