Has this computer ever worked? Is there anything you can tell us about when it stopped working correctly?
First of all, the computer won't boot if there's no RAM.
The green LED only means the board is getting power, nothing more. Fans spinning also means they're getting power, nothing more.
The board you mentioned has on-board video (NVIDIA GeForce 6100). Are you using this or are you using a separate video card? If you're using a separate card, make sure you plug the video cable into the right port (the video card, not the on-board).
Make sure the video card (if you're using one) and and RAM is seated securely and properly and all necessary power cables are connected (the video card may require a power cable, but can't say for sure without knowing what it is). If you've changed the RAM, make sure the RAM meets the requirements of the motherboard:
2 x 240-pin DIMM, support max. 2GB DDR2 800/667/533 ECC and non-ECC, un-buffered memory
To get to the POST (Power On Self Test), at the very least you need a working power supply, motherboard, processor, RAM, and an on-board video chipset or a video card. All other hardware (DVD drives, hard drives, mouse, keyboard, etc.) are not required to begin the POST which the computer does every time it turns on.
No POST or error messages/beeps could indicate a bad power supply, bad CPU, or something just not being connected correctly.
