So this is a slightly older Mac, and its been running perfectly up until now. I've got several OS's on the drives, but do have one SSD with a non-approved 10.12.5(there was a helper app that bypassed Apple's security) but now, the computer runs just fine for a few minutes, then freezes, and restarts. I have multiple OS's installed over the 4 drives, and regardless of what OS I start up from, I get the same result. I've also pulled out all the drives except the SSD, which only has 10.12 and a recovery partition. I even tried to re-download the OS while in Recovery, but Apple won't allow that since the OS and CPU, to Apple, are a unsupported combo. I've taken out all the RAM except for 2 1Gig sticks that I'm sure came with the computer. But I have rotated all of the RAM I have and still have the same problem. I've reset the PRAM numerous times, I've even reset the CUDA (I think that's what its called... the tiny button on the motherboard), I've removed all of the PCIe cards I've added, and even replace the original video card with a different one... and I've removed the disk drives as well. I've basically stripped this computer down to the very very VERY basics, and I still have this problem. It just freezes after a short period, and then shut downs for no apparent reason. I set this up to auto login, and launch the console, and there are a whole bunch of message that mean nothing to me.. I have an Apple Start Up DVD with Hardware Test, but the disc I have didn't come with this computer, so it doesn't run. I've started in the Recovery mode, and used Disk Utility to check the SSD... All OK I've started up in Single User Mode (Command + S) but only know of one command to run. (fsck -f), but it too passes... and then freezes. I'm going to take it out to my garage and blow out as much dust and crap as I can to see anything helps, but I'm not holding my breath. I'm halfway thinking this is a power supply issue, but am open to trying ANYTHING to get this computer running again. I've had Macs in the past that have had processor issues, and have experiences numerous kernel panics... but I've not seen anything like that with this computer.... which only leaves the power supply. Any ideas? Suggestions to try?