System Hangs

Hello, I am helping a friend restore his old computer that stopped working months ago.
Its a HP m8200n that had a hdd swapped to an 80gig(with windows vista). I dont know why the downgrade but thats what happened. Problem I am having is that it takes so long to boot into windows. Even in safe mode it takes forever to boot so I left it and about 10-15 mins it went into windows, everything was slow.
I opened up the tower and seen 2 sticks of 512 ram. Took 1 out turned it on, same thing. Replaced it with the other one and nothing happened. Ok so I thought bad ram. Used 2 sticks of my ram (an upgrade from what the other ram was) and same thing, extremely slow. That should eliminate the possiblity of ram failure(unless its the ports on the motherboard that are bad). I did test each stick of the old ram and 1 tested good and the other didnt load(that was the same stick that would not load the pc up)
I took out the hdd put it in my desktop and booted fine. no problems at all, so that should eliminate hdd failure.
I did manage to get a code on the computer saying 'bad cpu cooler, shutting down'. I switch the cpu fan with one I had. Worked fine but still wouldnt load.
I also managed to get some beeps, 2 short, 1 long. Looked that up and possiblity of bad ram, thats when I did the tests on the ram.
Now im stuck, could it be the motherboard failing? Bad power cable going to hdd?
Any ideas on what I should try next?
Thanks everyone! :wave:

update: I tested both sticks of ram 1 at a time, 1 good and the other gave me an error. I put the good stick in and reset cmos, tightented cables/wires and all and it booted fine. I put the bad stick back in to see if it was the ram and it gave me the error again. So I took the bad stick out, reset cmos and now it wont boot again. Any ideas on this? I am confused more than ever.

last update:I believe its solved. A mod can lock this or delete it.
Thanks