If you aren't getting the chance to get into bios, then you have a hardware issue. Does your computer make any beeps, or does the motherboard have a digital read out for error codes? If so, please relay what the beep pattern or error code is.
Try swapping out video cards. If you're using onboard video, try plugging in a PCI-E(or AGP/PCI... but hopefully your computer isn't that old). If you're already using a 3rd party card, unplug it and either use onboard video, or if that isn't available try a different video card. (This is all assuming you're a geek like many of us that have whole or parts of machines around that we can use for parts).
If not, then start unplugging things. First all of the hard drives and DVD drives. Boot it up...