The MB is working because it is giving the CMOS error beeps. Could be any number of reasons including RAM. Maybe try unplugging the system, remove the battery and reset the CMOS jumper. That would default the BIOS. If that doesn't lead to a solution, you would have to bench test the system with CPU, 1 DIMM RAM in slot 1 and the video card only (unplug everything else). If a bench test fails to solve the problem. Spare parts would be needed including RAM, video card and possibly PSU CPU.
If you want help list your system specs including CPU/MB/RAM/VC/PSU etc.