Still happen when in safe mode? Would be a good indicator of a software problem if the issue is not present whilst running in safe mode.
Good advice, do what this chap says..Use only one stick of ram and try it in each of the slots in turn to see if the problem lies there.
Make sure the CPU is not overclocked in the BIOS and set all the default settings. Then check the BIOS is running the RAM at the right speed and voltage if not alter it manually.
Have you swapped out the GPU ?
Also try running the PC with the minimum possibly plugged into the PSU to make sure its not that.
Use only one stick of ram and try it in each of the slots in turn to see if the problem lies there.
Make sure the CPU is not overclocked in the BIOS and set all the default settings. Then check the BIOS is running the RAM at the right speed and voltage if not alter it manually.
Have you swapped out the GPU ?
Also try running the PC with the minimum possibly plugged into the PSU to make sure its not that.