VGA port not working

[stinkyrossignol]

I have a old EMachines computer and i had gotten a new case and it was better than the one my computer came in. so naturally i tried to transfer the motherboard, the harddrive, cd drive, and power supply. After a couple hours i tried to turn the computer on and... nothing. it wouldn't turn on, so half an hour later of fiddling around trying to fix it i got nowhere. Then i transfered everything back to the first case and everything went back in smoothly so i got everything plugged in, turned the computer on and this time it turned on but the screen said "no signal". i am at a loss for words. this computer has only one output and no dedicated GPU so i have no idea. can provide additional details of necessery. i have tried three different moniters.