My monitor turns off and power button blinks after changing my graphic card.? Pls help ....?

i have changed my graphic card . After doing so , wen i on my system the windows xp booting screen appars and after the monitor turns off. The monitor switch blinks thts all.... I need a help.....how to solve this. Im using pentium 4 , 2.66 GHz processor , 256 MB Gforce graphics card , LG flatron ez monitor and 1 GB ram. Help me to solve pls .... Vry urgent !!!!