I have an old Motherboard (P5N-D) that I want to reuse for a machine that I'm building for my sister to play TF2. She needs a new hard drive, and I'm looking at one that has a really good capacity/performance per dollar ratio, but it uses sata 6.0gb/s and the motherboard is only sata 3.0gb/s.
Will they work together if I plug them in?
More aboutsata backwards compatible
Yes, it is backward compatible.
And there is no difference in performance for hdds.