nommad,
You know, I hear that suggested a lot, and maybe it's true to a large degree, but hell, I can't afford a dedicated music computer, I have to use it for everything. And (knock on wood) so far it seems fine. The thing is to avoid letting apps load up all kinds of crap that attempt to help you. For example, the Office Toolbar, or some scheduler thing, or Find Fast... but Windows itself will do a lot of that with a standard install, too. If you follow the basic rules about keeping nothing running save your audio apps, I think you will have very little trouble. I'm doing that, and so far so good. You might also look at the Hardware Profile thing -- you can create another profile that has certain devices, like a scanner, or a modem, say, disabled. I needed to do that in my previous machine to get reasonable performance (I turned off the network card and modem). In my current setup I haven't had to do that yet.
-AlChuck