A friend want to buy a Windows 7 Home Premium OEM for his PC. So far so good. But the PC is both a gamer-rig and a "family"-PC, and from XP he is used to have 2 Windows installations on the same PC, but on different harddrives, so when the "family"-installation is booting it can't show or destroy his gamer harddrive (used to be marked as "hidden drive"), and when he boot up to game, he has a very tiny system setup running absolutely the least in background, leaving as much as possible power to his games.
Now, I think he will run into troubble with an OEM version of Windows 7, as with 2 different installs on 2 different harddrives, he must activate Windows 7 OEM 2 times, but from different controllers ("family"-install is 1 harddrive, and his "gamer"-install is RAID 0.
Besides these possible troubbles, is it legal to have to installations on one OEM CD-key? It IS the same PC, and they can of course not run on the same time, but it will require 2 activations with some different hardware, most of the hardware are the same though.