Windows XP: over 1GB
But what features does it have that require such ridiculous amounts of ram? It seems to me like it aint coded to efficiently use ram. You can use a lightweight OS like AmigaOS for most of the same tasks as a Windows pc, so what is the benefit of it using so much more resources for doing the exact same task?
Windows is in my opinion bloatware...
Edit...One more thing, if you really hate Windows that much, put your money where your mouth is and do what I did, buy a mac, actually, buy several, as in my case.
OSX is pretty slow and resource hungry as well..
Though the real reason for me having a PC, is due to the fact that i like to play a game every now and then. I use linux whenever possible though..