At PDC a netbook with 1GB of RAM was showcased running Windows 7 just fine.1GB of RAM isn't much these days, but still I kept wondering how much RAM does Windows 7 really need? I created a VM and gave it 700MB of RAM. It booted just fine and windows idle with no apps were using 360-400MB of ram. (That is just 50% of the total!)Then I decided to open 10 explorer windows just to see what usage it would go up to. With the 10 windows the ram usage went from 400MB to 425MB.
But I didn't want to stop there, I wanted to find out when the prefetch-applications stopped and try to find the "static" amount of RAM that Windows 7 needs.* I shut the system down and set the RAM to 500MB and booted back up. Now the system used 290MB with 210MB to spare. Then i rebooted it with 300MB available RAM. To be honest, the boot wasn't happy about just getting 300MB to work with and the boot slowed down for quite some time. But when it finally got into the system it went to 250MB of RAM at idle.