I've been though this process with Win2K several times. Every time I have done it, I have simply removed the chip and started the computer. Windows 2000 automatically recognizes that it only has a single CPU and works accordingly. I've never actually gone through and changed hardware settings or anything. When I got another CPU, I pu it in, started the computer, and everything worked fine. Win2K is pretty nice about the process, it doesn't b%#@h and moan every time you change hardware, like Windows XP Pro does. Going from MP's to Durons, on the other hand, is a different story. You have to totally reinstall Windows if you do that.