Constant Restarts + Won't Boot From CD

Earlier today I restarted my computer. Right before starting to load the Log In screen, it restarted. I have tried to start it in all three Safe Modes, and with the Last Good Config, and it won't boot.

My computer also won't read from the CD-Rom. Since I lost my Windows XP CD, I got a copy of the CD somewheres else, and my computer won't boot it. I also burned it with Nero, and made it a Bootable CD. My computer would boot this, but it's not much help since it won't let me access my c:\ drive or run any .exe's.

The computer I'm on now also doesn't have a Floppy Drive.

What should I do?