seems a bit of a waste of time setting up raid for just 2 hard drives
i got 2 hdd's and four partition's on my pc
(system,programs,data and backup (backup is on seperate hdd)
just plug new hdd into pc, make sure old one is above new one in boot order in bios and it should auto detect it
(talking about raid, there are diferent types that do differnet things, with only two hard drives i asume that you want one for backup's, if this is the case better to not use raid)
not much point using raid unless you want redundant data or use a few to get beter transfer speeds, using it for higher transfer speeds increases the chance that you will lose data if one of the hdd fail
in raid 0 for example, it is fast becasue it splits the data between all the drives but if one ofthe drives go say bye to your data