If your RAM is connected properly (must be since there are no beeps) that leaves 1 of 5:
1. Videocard - Is videocard installed properly

Is videocable connection to your monitor connected properly
2. Connections - check your monitor's power cable - it may probably be loose, or busted. Replace the monitor cable with one that's working if possible then try it again. Are the cables and power supply connectors on your harddrive properly connected to your motherboard and PSU respectively

Are the LED and power connectors in the right motherboard slots
3. Power - there's enough power to run the fans but not enough to run the restof your computer. Either try a PSU with a higher wattage or go to another electrical outlet and try it there (maybe a faulty power outlet).
4. CPU - Take out HSF, Lift the ZIF lever and remove the CPU gently. Look above and below it; are there any scratches, cracks, marks - anything out of the ordinary

If then your CPU is busted; time to get a new CPU
5. Motherboard - If everything from 1 to 4 is okay, then it's the motherboard. No choice left but get a new one
Hope this helps