Newly built custom PC wont work. PLEASE HELP!

I recently built a PC for my friend, my PC is custom as well. when i built my PC i did run into a few errors, they were quite simple to fix though(exp. MB touching case. etc,.) everything on my rig was new except a few minor items such as HDD and the DVD Player and the same situation with my friends PC but the case is also used as well.

I put all the parts together and doesnt work. i replaced all the major parts (CPU, HDD, PSU, RAM etc,.), because i did not have a ferrite ring for the case i bought ferrite clamps- still doesnt work. everything is where it is supposed to be on a PC but it still doesnt work. what am i supposed to do?