If you put some time into it Vista will run fairly well on a PC running 1GB of DDR2 RAM. I've disabled all of Window's default security features and added my own plus optimized the hell out of the files. Never stick with stock.
Typically when I boot up, Microsoft Windows Vista is using about 12-13% of my installed physical memory. I am running Ultimate Edition x64 on a system with 8GB of RAM.
On a fresh boot, it uses around a gig, but after about a week, it is at about 1.5-2GB used. But when im working, it sits at around 3GB used, running Vista 64bit
Hah, I'm at 4 gigs now, and I'm screaming to have 8gb or more! Its better, but don't expect much.. :-( Idle I can get it down to about 35% of 3325mb but when I'm actually using it. I tend to swing 60% to 75%. Anything more and you start using pagefile I think? The thing just bogs down. a gig of ready boast ram does nothing, lol.