Kariudo wrote:XP: 64MB [minimum] 128MB recommended
XP has a hard time running on anything less than 256 (unless you're in safe mode)
ive ran XP pro fine on 64MB (works better with 256MB) ram compaq deskpro's
vista ran fine with only 512MB ram, Ive gamed with it, as well as a bunch of other stuff with no problems or low memory warnings
AFAIK you're both right. XP Service Pack 2 eats up the computer's resources like a fat kid at Charlie's Chocolate Factory and 256 is the bare minimum for XP SP2 to only crash every other hour, but if you don't run SP2 and disable some of the eye-candy (which is very poorly coded, since it wastes way too much RAM for simple stuuf like shading under icon names on the Desktop - MAC OS X and Beryl do a lot more for a lot less) then 64MB will run (although I don't think you can call it very stable on 64MB - I've never tried XP on it, but Windows 98 crashed a lot on me with 64MB).
I've just installed a little package on my brother's computer that gave the full Vista look to his XP set - the sounds, the icons, the taskbar thumbnails, the glassy windows and even the desktop widgets (practically everything but that 3D window-spinning thing that can replace Alt+Tab) and the RAM load increased by about 50MB. Actually running Vista is bound to be heavier than theming XP, but based on this and the fact that most of the changes were visual, I don't really see why it would be so much heavier.