I want to point out that I am not very educated on computers. However, I managed to at first buy my friend's old PC, a HP prodesk 600 g1 twr. It wan't performing as I wished it would, and I got a sweet deal from my friend to buy his old GTX 970. I told my friend the specs of the PCI port, he said it would work and I believe it will, so i bought the 970. The problem is just that the new PSU I bought in addition to the graphics card, has a 24 pin main power connector, but it's not the 970 that has problems... The PSU's 24-pin main power connector does not fit in to my 6 pins on the motherboard.
The GTX 970 also has one 6 pin "socket" and one 8 pin "socket". I wonder if both those have to be connected for the GPU to get its power.
I also wonder if there perhaps exists some sort of adapter for the 24-pin, so it would fit in the 6-pin on my motherboard.