I just tried to install more RAM, a new heatsink and new GPU. When I try to boot up my PC it starts fine but after a couple of seconds it shuts down and automaticly starts again after a couple of seconds. After that it seems to run fine, but the monitor is just black (I think it goes in to sleep mode because it thinks the PC is off. I've tried multiple ports in my new card, my old card and my motherboard.
The new RAM sticks don't seem to be the problem either because I tried without the new ones.
PSU: Silver Power SP-SS750M 750W
Motherboard: P8Z68-V PRO/GEN3
CPU: Intel i5 2500k LGA1155
CPU Cooler: Noctua NH-D14
Old GPU: Gainward GeForce GTX 560Ti 1GB
New GPU: EVGA GeForce GTX 670 4GB
The new RAM sticks don't seem to be the problem either because I tried without the new ones.
PSU: Silver Power SP-SS750M 750W
Motherboard: P8Z68-V PRO/GEN3
CPU: Intel i5 2500k LGA1155
CPU Cooler: Noctua NH-D14
Old GPU: Gainward GeForce GTX 560Ti 1GB
New GPU: EVGA GeForce GTX 670 4GB