Thanks guys. Yes I am upgrading an old system.
I was told that my motherboard is '4-pin' and that the power supply is '8-pin', I don't know what this means, but am I safe here too?
This upgrade is for my girlfriends computer. I have recently bought the same GPU and PSU for my own computer, which has a different motherboard. The GPU and PSU work fine with my computer (Acer Aspire M3970 ).
Taking this into consideration, do you think I need the CX600 for my girlfriends system because her motherboard is a little older than mine? Or will the CX500 be ok with her system too?
The CX500 is fine. I was just suggesting the CX600 because some sights have it listed for the same price as the CX500.