Good Morning!

I have a few pretty big startup issues with my dads computer.  I'm not too new to fixing a computer here and there, but I am stumped this time.  Originally the only symptom was random shutdowns.  This had happened once before and it turned out to be an overheating issue and a simple dismantle and clean up FIXED it.  So, that's what I did, and I must have done something very wrong, although I have checked and rechecked and cannot find the issue.  I do believe it to be a hardware issue, but am not 100% on that.  I have listed the symptoms/occurrences below:

On start up, I get one seeming randomly selected error

BLACK screen with the statement "The file is possibly corrupt. The file header checksum does npot match the computed checksum"

A random restart sometime during the startup process

BSOD (Sometimes a Crash Dump) with  : STOP : 0x00000124 (0x00000000, 0x90503024, 0xB2000010, 0x00010C0F)

A solid black screen (the GPU display comes up, but then just sits on black screen for over 30 mins, until shut off)

Windows Startup Recovery (Recovery essentially does nothing)

System fan failed to start (I currently have the casing open and all fans are running as usual)

Normal startup, but will shut down after 10 mins of operation.

Now for my already attempted solutions:
Reset bios by reseating CMOS plugs.
Reseated all RAM individually on separate startups.
Disconnected graphics card and used onboard output.
Tried to update the BIOS, Computer doesn't stay on long enough :/
I have tried using Startup Recovery option, but I get a message that it could not fix the issue.

Now for the all important specs:

HP Pavilion a6230n
Corsair GS700 PSU
PNY XLR8 9800 GTX+ 512MB GPU
8GB RAM
AMD Athlon 64 X2 Dual-Core Processor 5600+

Thank you all for any and all help you could possibly give.  I am only in town for the holidays and would love to get this working for my dad again.How old is this computer?

Do you see any leaked capacitors on the motherboard?I see no popped or leaking caps.  I am not 100% on the age, at least 5 years, I would have to say.Just a guess, but it could well be the power supplyI do have a spare power SUPPLY around here somewhere, but, if I recall, we rid of it because it wasn't quite enough to power the GPU.  I will take a look though, and swap that out.You can then remove the addon gpu, use the on board graphics and use the spare power supply for the diagnostic purpose.Alright, so far so good.  Which diagnostics should I run? I'm not entirely sure what to do at this point xDDon't run any diagnostics at this point. Just see if the power supply solves the problem for starters.Alright, I will use the computer as normal, to see if it wants to shut down on me.Well, So far so good.  I will keep it on and stress it every now and again and give you guys and update LATER.  Only time will tell at this point ^_^At some point you're going to want to run chkdsk /r because of all of the anomalous shutdowns. Don't do it yet though, since you don't want the system to shutdown in the middle of running checkdisk - that can cause major problems. Once you are confident the system is not going to shut down, do the following:

right-click on a command prompt icon and open as administrator. In the command prompt window type: chkdsk /r (then press ENTER). You'll be told the disk is in use and asked if you want to run checkdisk on the next boot. Say yes, exit the command prompt window, and reboot.I decided to go ahead and a restart to make sure it was starting up alright.  It did not shut down on its own after waiting for a while.  I am now getting this:

Award BootBlock BIOS v1.0
Copyright junk

BIOS ROM checksum error
Keyboard error or no Keyboard present (my keyboard is plugged in, but wireless, so it may not be communicating)

Detecting IDE ATAPI device

Detecting Floppy drive A media
INSERT SYSTEM DISK AND PRESS ENTER

haven't seen that one yet, and on a second restart the desktop was on, but no display.  The monitor shut off due to no connection (It does turn on automatically if a connection is established.)

On a third and fourth restart everything came up as normal.  I will continue to restart to make sure the other issues are gone though.  No Blue screens yet ^_^You probably want to replace the motherboard battery. Let's see if that helps the boot process.Will probably have to go and get one.  Don't think I have a spare.While it's refreshing to have someone keep us closely posted, you really don't need to report everything every step of the way .