I'm really new to this forum and hoping someone can help. My friend's computer started blue screening randomly last week seemingly out of nowhere (no lagging, no blue screens prior to that day). It kept reporting different errors:
There was also a POST and some memory related errors from what I remember. He tried rebooting the computer and got different errors almost every time while trying to run tests/get back on to windows. Sometimes it would get to the desktop and others it would freeze while in the BIOS. After about an hour on reboot the computer stopped going to BIOS and now has power but there is no video(it seems to be running but won't actually post or boot, not that we can see). We've swapped out RAM and purchased a new power supply but it's still the same. He got a new mobo/CPU a few months ago before the problem occurred and switched both of them out for the old ones and nothing changed. He unplugged the monitor from the video card and tried to use the onboard and nothing there either. We're kind of stumped here.
I would have suspected a dying motherboard from your first symptoms, and then ram or psu, but you seem to have covered all the bases. Presumably even installation in the case can be excluded since you say you've tried the previous motherboard and cpu.
My technique, already mentioned by Shinma, to test a used motherboard or cpu, or a new one prior to a build, is to sit the motherboard on a non-conductive surface, usually a folded newspaper, and connect only what I need to get into the bios: board, cpu and hsf, ram, psu, monitor, keyboard, and a switch on the motherboard pins. Try both (or all 4) ram slots, one stick at a time. Beyond this all you can do is swap these minimum parts, and it sounds like you've done most of that.
When you get the early indications of problems, as you did earlier, one of the first things I'd do is to boot the Ultimate Boot CD. From this, which will exclude the hdd and the OS as issues, you can run Memtest86 on the ram, and run the manufacturer's test utility on the hdd. If those are okay, a boot to a live linux cd will tell you if you have an OS issue. (Both these can be run from a flash drive now, of course.)