A 5 yr old hdd is likely to fail soon. It would be fine as a storage as it would get less usage. So maybe get a 120gb ssd.
Sata 2 is not called sata 3 and it's Gb/s not gigs per channel, hdds don't have channels per se and Gb/s is a measure of bandwidth. Sata 3 is also not called sata 6. They may be referred to as sata 3Gb/s and sata 6 Gb/s but the number alone refers to version. Otherwise you are just confusing everyone. Gigs also usually refers to gigabytes when this is in gigabits.