I turn on the computer and it does not load or nothing. the only thing that lights up is the hard drive light and it stays on.

Hi,
I don't know how computer technical you are, but it sounds like you know a thing or two about them. So here's the best way to find the problem:
There could be many things that could stop the board from fully booting, Determining what is wrong is like detective work. What I do, is open up the case and take everything off the board to start. Then add the minimum to start a board to see if it will start. That's one drive (cd, harddrive or otherwise) the CPU, a graphics card (only if required) and one bank of memory. (which is not required, but it helps avoid beep codes) Also, make sure you have your pin's set on the board absolutely correct, or that could be your problem to begin with. If your going to load a ide drive, make sure you set your pin setting correctly on it, meaning the drive (IDE or EIDE) your putting on the board is set to Master, or Cable Select if your using the cable placement method.
Now, turn it on, and you should get the power supply on, and the cpu fan going. If they start, then make the next step to have the single drive be your hard drive, and see if it boots. If it boots, then great, open Bios and make sure Bios is reading the board and all things are fine with it. If so, what ever you put on next make sure it one at a time so you can identify what it doesn't like.
In the situation where the CPU or power supply don't power up, it's then either one of the first elements. The CPU, Power supply, Ram, Drive, graphics card (if required) or the motherboard.
The next step is to replace each one of the first five, starting with the Ram Chip, put another like chip in and see the results. Then do the same thing to each of the remaining 4 components, the graphics card (if required), then the drive(cd, harddrive or otherwise), on to the CPU, and last the power supply. Hopefully something will show it's ugly way to make a change. Also, on the drive (IDE, EIDE or SATA) , try a different cable to make sure it's not that, Most people say that they don't have additional components to do this with. I understand, but if you replaced something like a new hard drive, then you probably still have the old one. In most cases you might have a friend (Geek) that might have some spare components. If not, then you may have to make an investment at the local try's or computer store. Keep the reciept so once you find out what it is, you can return the rest of the stuff you don't need.
Now If no changes happen after all that, then I take it one step futher and usually get a like (doesn't have to be exactly the same, just capatible with the components so they can be tested on) motherboard that I can test the first four, and make sure that they really work. If after that and you have tested all of the components and they all work, then it's save to say you have a bad motherboard my friend. It's a lot of work I know, but it's the sure fire way of finding out what isn't working.
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Good Luck