Hewlitt-Packard motherboard suddenly not POSTing after messing w/ hdd's and screwing up system files

Enhanced Interrogator

Mar 23, 2013
So this is the PC I've been using for the last 6 months or so, a used HP business-class PC with a i5-3470k. I had 3 HDD's hooked up to it a couple days ago, moving around files to get ready to put on my new PC. In the process, I had messed with permission settings and ended up screwing up some system files, so bad that the start menu wouldn't open.

No big deal, I thought, not going to use this PC anymore anyway, I'll just reformat before I sell it. Anyway, next day, I go to boot it up, and it won't POST, or at least I can't get a video signal (with integrated or graphics card), fans will always spin up though. Tried different combinations of RAM and no RAM. No RAM gives me the beep code for memory error, and with one stick I've gotten it to boot a couple times, but I always miss the BIOS prompt and since my HDD's aren't hooked up anymore, it just goes to the "no bootable device" screen, then when I reset, it won't POST again.

What do you guys think happened? Did my memory controller die all the sudden? Could the corrupted system files have somehow hurt the motherboard? Is there some other issue that can occur with OEM UEFI systems from companies like HP that I'm unaware