It seems as the parts are from different suppliers you will need to diagnose the exact component/s so they can be returned .
Are you sure the power supply stops like does the power light go out?
If the computer is just resetting , when it does fault press delete to enter the bios and check the voltages and temps. is anything out of the ordinary?
Is there any way you can get the computer to always do this . I mean like say " every time I plug my cellphone in to the front usb port it restarts."
Also check windows logs at the time to see if there is anything logged.