You can partition your drive into 2 or more if you wish, creating C and D or more. Or you can use 2 separate drives. As far as raid goes, Raid 0 is called stripping where pieces of data is stored on both drives for faster access creating faster game play and decreased boot time. However in Raid 0 if one drive fails all your data is lost. Raid 1 is called mirroring in which whatever data is on drive 1 will be on drive 2 in case of drive failure. If one drive fails then you still have all your data on the second drive and its just a matter of getting another drive and hooking it up and the raid rebuilds itself. As far as you needing or wanting raid? It depends on what you want. Raid 1 has saved me a few times but I no longer run it.