when i start up my computer, it goes to the 1st and 2nd screens with no problem but before it loads windows, the screen goes black. if i press anything the computer restarts. i tryed starting it in safe mode, safe mode w/ command prompt, start w/ last working configuration, and in vga mode but all of those have the same reactions. i get a single beep like always when it starts up. i have started it before and it was fine, this isnt a new computer.

I am assuming:
1.) Your hard drive's IDE cables are not connected properly (loose, slanted, etc.).
2.) Your hard drive has a conflict with another hard drive.
3.) Your hard drive's jumpers are not placed correctly.
4.) Your hard drive is not receiving sufficient power.
5.) Your motherboard is not configured to accept your hard drive.

In the worst case, either the motherboard or hard drive is dead (unlikely, very unlikely). I recommend checking the connections on the back of the hard drive and the motherboard, so it's a simple procedure. You'll also want to check a "beep" forum regarding the signal the motherboard is trying to give you.