There are a few things that can cause this. 1. One of your RAM modules (rectangle with cmall black rectangles on it) located on the motherbarod is bad. 2. You have WAY too many USB devices atached to your system, and there aren't enough IRQ's to go around.
TRY THIS: 1. Remove all the RAM modules, and try booting with them one at a time. if none of them work Then (HOPEFULLY) it's not your ram. (if it Isn't the second one, it could mean the RAM slots on your motherboard are bad, and misreading, or all your RAM is shot.) 2. Remove one USB device at a time, starting with anything plugged into an external USB Hub. And, as a future tip, never boot with any USB hubs, or external storage devices present, as they're known to cause issues with the boot process due to it's method of reading, and writing files to a drive.
What I mean by that, is that sometimes, if a removable drive's inserted upon boot, or while installing an operating system, it could have the boot files written to it, then when you take it out, you no longer boot, because you don't have the files to, so as a precaution, never have external drives or flash media inserted at boot. Dracconus