My dell monitor go into power save mode after startup

Hello , i've got a problem that turned my life miserable with my dell vostro 270 i bought it 6 months ago , the problem is that when i install the nvidia driver and reboot the pc windows loads up then it give me this message "entering power save mode" i tried all the solutions that i found in my search , the seller told me that my resolution is set too hight that my monitor cannot display so i should start with base video mode but same problem ,im getting bored of trying, please give me a new solution im facing this problem for 6 months!
My specs btw:
Dell inc mother board
intel core i3 2220 3.3 ghz
8 gb ram DDR 3
Nvidia geforce GT540 4 gb DDR3
Windows 7 sp1 proffesional x64