Yes, the memory will fit in your motherboard (ASRock N68C-S UCC). But it depends on your processor whether the memory will work. Only AM3 socket processors are capable of running the DDR3 memory. Your motherboard supports both DDR2 and DDR3 memory. DDR2 and DDR3 will not work simultaneously. Hence, make sure the whether the existing memory is DDR2 or DDR3.