I'll start from the beginning. A few months ago I bought my brothers computer, not the best thing in the world by any means but about 100x better then my computer which was built in 99 .(Side note. My brother had been having problems with the computer shutting off by itself so he bought a new power supply for it and was going to put it in the new computer he was buying and leave me with the old one, well when I first got the computer and hooked up it wouldn't come on so we had to put the power supply he was gonna use for his new computer but even when we did that it was still restarting itself) At first everything was awesome, I could actually run counter strike source higher then 10 fps! lol. So after 2-3 days of having it I walked away for maybe 45 minutes (coulda been longer, its been so long I don't remember) and when I come back the screen is black, as expected. I move the mouse to get it out of sleep mode or whatever you want to call it but it doesn't do anything. I turn the monitor off and then back on and it says "no signal input or cable maybe disconnected" well something along those lines anyway. I restart the computer but still nothing.(When I turn the computer on the fans start and the lights turn on but there is no beep code and nothing comes up on the screen) I tried putting my old video card in and that didn't do anything either. So I give in and take it to the computer guy, he has it for 2 weeks until he looks at it, and when he finally did look at it all he did was take the ram out and put it back in. Well somehow that fixed it, but after having it for about 3-4 days I walk away for 2 hours and its doing the same thing it did before. So I try taking the ram out and putting it back in hoping for some insane reason it would work, but it didn't. I'd had enough of messing with that POS so I just gave it back to my brother for my money. Its been a few months since that happened like I said, but now my brother has given me the mobo, cpu, and video card for free, but it still has the same problem. Any ideas on what I'm gonna have to do to fix it?

So all you have now is the motherboard, CPU can video card? No RAM? No PSU? If that's the case, there's no way to trouble shoot anything.

The problem is the original problem could have been caused by any number of things; failing RAM, leaky motherboard capacitors, failing motherboard, failing video card, failing PSU, heat, malware...

There's nothing to go on here. If you had a compatible computer, you could test the RAM (if you had some) and video card. You can inspect the motherboard for leaky capacitors. Leaky capacitors are a common cause of sudden system lock ups and reboots. Look for white to dark brown dried foam leaking from the tops or bottoms of the capacitors. The capacitors look like tall soda cans, many of which surround the CPU socket. Bulging capacitors are a sign leakage is about to occur. A motherboard with leaky capacitors can be repaired, but generally it is more cost effective to replace the motherboard.

I'm sorry I didn't explain that well, I was tired lol. When he first gave me the computer it was case, PSU,CPU,HDD,video card, RAM, and mobo. Now he just gave me the motherboard, cpu, video card, and ram. So I'm using my PSU and my HDD with all of his old stuff, and I doubt that I don't have enough watts in my PSU considering I started having this problem when I had a perfectly working PSU. FYI the PSU im using now is 20 watts less then the original one he was using. Also I did quite a number of tests before giving back the computer. Like I said in the original post I tried putting a different video card in but that didn't do anything, I also tried having 1 stick of ram in the mobo at a time and that didn't do anything either, and last but not least if the problem was the cpu video card or ram etc I'd be getting a beep code, but I'm not, I'm not getting anything at all except for the fans and lights turning on. Hope that helped.

Well, since you've given no information on the CPU, RAM, or video card, I don't know if your PSU has enough power!

I still don't know if you have a case or not - the only concern there, from my standpoint, is a speaker. If not built on to the motherboard, and most older motherboards do not have a speaker, then you need a case speaker connected to hear any beep codes.

However, what I would do if that came across my bench is pull it all out of the case and set the motherboard up on a hard, non-conductive surface. Connect the CPU, video card (if not built into the motherboard), and 1 stick of RAM and a known good monitor. No HD, or any USB device. I would probably pull the battery for 30 seconds to reset the BIOS. I would use a known good PSU. Upon power up, it should beep once, display the video card's splash screen and give the prompt to access the BIOS.

If not, then the CPU or motherboard (or both) are toast.

I've tried hooking 2 different monitors in. I'm not sure the exact name of everything but the video card is a geforce 5700 (lol) 2 512 sticks of ddr ram and the cpu I'm not quite sure, I think it might be an amd with 2 ghz of speed or somethin like that and the PSU I have in there is a 320 watt. It's not that old of a motherboard, I'm sure it does have a speaker because the motherboard I was using on my old computer had a built in speaker so I don't see why this one wouldn't. Also if I remember correctly I had the beepcode everytime it turned on before the tihng broke.

That help at all?

320Watts should be fine for most CPUs with that video card.

I'm sure it does have a speaker because the motherboard I was using on my old computer had a built in speaker

Were they the exact same model motherboard? If not, then you cannot be sure. It is not uncommon for motherboards to not have a speaker. If you can look on the motherboard for a make and model number, we can look it up.

Getting the same results with two monitors only proves the 1st monitor you tried is not broken.