HP LCD moniter stops working after graphics card mounted
 

I just upgraded my pc power supply to "Ultra LSP750 750-Watt Power Supply" and i tried to add on this card "PNY XLR8 GEFORCE GTS 250 1024MB GDDR3 PCI-E, DVI-I as soon as i turn on the pc everything works except for the moniter, it does not receieve any signals. please help me (btw the moniter...