One thing you can try right now is to disconnect power to everything except the core components, ie., all optical drives, floppy, non-os hard disk, card reader, NIC,.. See if that allows your computer to boot up. If it still doesn't then try the video card on other pc. In the BIOS, besure to allocate 0Mb to shared video. With only 256MB you need everything to run it correctly. GL.
