When this happens, it could be a number of things: RAM, CPU, Power Supply, incorrect grounding, or bad motherboard. I would check the simplest one first. Try switching out the RAM or booting with one chip. If that works, then it's bad RAM. If not, then check to see that the motherboard is screwed in tightly and that it's not touching anything else on the case. If that doesn't work, try taking all your cards out except for the video card and boot it up with the hard drive only (disconnect the CD/DVD-ROM drive(s) from the power supply. If that works, then put in one card at a time until you can get it all up. If it doesn't work, or stops after you add X amount of cards, then it's probably a bad power supply. Switch in a new one and hopefully it will boot. Otherwise, you'll have to check out the CPU or motherboard to make sure that it's not damaged. Hope this helps.