I have 2 hd's myself.
First one is for oses. 1 partition winxppro, 1 partition fedora core 3.
2nd hd is just full of games n' apps. if my main hd fails? so what? reinstall an os or 2, not the end of the world for me.
I'm sure it'll work with the oem key. I had an old compaq with a compaq oem of windows98se. Borrowed an win98se cd from a bud, used the compaq oem licence, and worked fine man. And compaq's more strict than dell I bet, so if I could pull it off? you can. To the computer: it doesn't care what cd you use man, as long as the licence is legal. That's all man. I ain't gonna tell you again.