Raid don't work like that. You need 2 drives the same size, if you were to raid those 2 drives together you would have a total of either 120 gb if raid 0 or 60 gb if raid 1. if you want more drive space you will need to buy another 160 gb to have a total of 320 gb if doing a raid 0 or 160 gb if doing a raid 1 (mirroring) which means whatever data is on one drive will be on the other one as well, in case one drive dies.