For some reason my laptop keeps restarting after 3 seconds. I know it restarts because the power light comes on then goes out again. After it shuts off it comes on again by itself and does the same thing over and over. The only way to make it stop is to hold the power button or take out the battery. The display doesn't come on but the fan spins and I can hear noise from the cd rom drive. I have tried reseatting the ram ( even replaced it with new ones), taking out the hdd, taking out the cmos battery for 2 min, and even resetted the processor. Removed the battery with just the charger in. Nothing seems to work. Please help!

It might be the battery or charger. It might just be that your laptop is too old. Take it to the store and ask them.
(eg. If it is an apple_ mac, take it to the Apple store)

Have you reseated the RAM? Do you get anything on the screen?