Start up my computer and nothing shows up on my monitor

[logopogonogo]

So recently I took a pre built pc and put it into another case and when I press the power button the fans turn on and only one USB works and it's on the motherboard and the fan on the graphics card turns on and there is no picture that comes up on my monitor and I checked the hdmi chord and that's not it also when it's turned on if I press the power button to turn it off nothing happens I think it might be the mother board but I'm not completely sure

 

[Scottray]

Unplug the PC from the wall socket. Then, remove the button cell battery for a minute. Put it back in and reboot. This should reset the mobo.

 

[logopogonogo]

there isn't even a start up beep