cleaned cpu heatsink and moved ram now it wont start

Hi everyone i could use some help
i just took off my cpu heatsink to clean it out a little better because my computer was overheating quite frequently. My computer also hasnt been recognizing a stick of ram every time i turn it on so i rearanged my ram to see if it would fix the problem but now it wont turn on. When i hit the power button all my lights and fans turn on, it makes the same noises it always did when starting up so i thnk every thing else is on aswell but my screen just stays blank and no lights flash on my keyboard.

thanks for any and all help