PC Freezes at BIOS, Restart, Same problem. Pull the plug, Fixes temporarily.

I turned my PC on this morning and it froze at the bios again. I restarted and same result. Yesterday when I turned it on it didn't even load the screen or the mouse/keyboard, and another time it loaded the screen and mouse but not the keyboard. I think i am having some sort of compatibility with my hardware because Ive been tweaking everything recently. The main issues I have been having was 1 of my 1tb HD's was locked in Max security and with much toil I was able to unlock it with hdparm commands in Linux terminal, then I had another HD that was only showing 128gb total capacity in disk manager/bios etc. and again after much toil I found it had an HPA on it so after much research I was able to remove it with another hdparm command. Then there is the issue with my rams. I have 2 dual rams 8gb each that work together but the pc came with more different 8gb rams that are not compatible with the first 2, so I can either have 16gb ram that work @ 1866mhz or 32gb ram @ 1333 on a different clock setting (9,9,9,24) I think the problem might be the rams when it comes to booting the system but the problem with no booting the keyboard /screen/mouse came about when i switched to just 16gb @ 1833mhz (what the dual rams were specified for) anyways, so to fix the problem that time I had to pull the plug and re-boot and then it booted fine. This time after trying to reset it kept freezing at bios so I pulled the plug and then I got it to restart and load windows. Could this be something to do with my cmos battery? or possibly my mobo is defective? or maybe the rams arent working properly with my mobo? Ive also seen posts about similar problems where it was the Hard drives not readings the boot sequence properly etc... When I did pull the plug this time I also pulled the other Hard drives (the ones that had the problems before) Also I set those 2 harddrives up in GTP on spanned volumes while my boot drive is on MBR. could this possibly cause that problem? Oh and on top of this, I should mention before I go any further, I just bought this computer 2 weeks ago online from a community marketplace (kijiji) so anyways the cpu was running extremely hot before and it was running just above the maximum which is 70*C. it was running at about 73*C at full load so anyways I pulled the heat sink out and found a carpet of dust in the bloody thing so I cleaned it out with some isopropyl and reapplied some arctic silver 5 thermal paste just the other day. So could that possibly cause these problems? My computer runs really cool now and never goes over 50*C at full load in a bench mark. I have so many different variables that I have been working with so Im finding it really difficult to deduce the problem. Anyways, all feedback is appreciated and thank you in advance for taking the time to read this.