Powersupply could be the problem.
Do your simple mobo troubleshooting:
Remove from case. Place on foam or whatever.
Remove all cards.
Disconnect all drives.
Check jumper settings.
Reset CMOS.
Leave 1 stick of RAM in. Make sure seated well.
Install video card, make sure seated well.
Try.
If nogo, try RAM in another slot.
Try another powersupply.