Mouse, Monitor and Keyboard wont power on... :(

I recently took apart my DVD/CD drive to clean it. After i put it back together and reconnected the power cable and data ribbon, i plugged the computer back in and powered on as always. The moniter said "no signal" and the lights on the keyboard and mouse didn't come on. ALso i didn't hear a beep as there normaly is on power up. The fans are all still spinning but slightly slower then normal it seems. I checked the RAM, Bios battery and even tried a different PSU, still no luck. Any help would be really nice. Thanks in advance.