first custom build computer! need help...

[TypeZ]

No need to format anything. You can actually use an old windows installation for a new PC but it is not recommended as it can cause problems. The easiest way to find the problematic part is to remove all stuff that isn't needed to go into the bios screen(HDD, DVD-ROM). After that reset the bios either with the button for it(if there is one) or by removing the bios battery for a few seconds. Then you might want to check if your GPU's fan spins up. You can also try a different PCIe slot for the GPU. Make sure all power inputs on the mainboard and GPU are connected. It might also be a loose contact so try moving the connectors a bit when the PC is off.

okay. how do i remove the battery or reset bios?

[Coldfire]

okay. how do i remove the battery or reset bios?

Search for "Clear CMOS Jumper" in the manual. It's a small jumper on 2 of 3 pins(the outer is marked with a 1) which has to be moved to connect the middle and the other outer pin(not the one marked with a 1) for a few seconds. Do not do this when the PC is running.

So my hdd with the old window 7 is fine?

It could be. At least it won't prevent you from seeing anything on your display. You will know if it works or not after it either started up properly and installs new drivers or shows you a BSOD on startup