|You mention "Memory crash" in the body of the question, "Power Supply" "graphics crash" in the tags. You mention replacing the CMOS battery which might have been needed, but would not effect the memory or graphics performance. The you mention " 'It' (?) also turns off all external power..." which is not clear at all.|
Please explain completely the problem and what you have tried.
If you are having trouble with your memory (RAM), run Memtest via a bootable CD to test your memory for errors. Replace if you have any errors.
You have to be a little bit crazy to keep you from going insane.