Windows 7: SonyVGNNS190D/S VGA External Display Connection problem

The problem is that when I connect my laptop which is a Sony model VGNNS190D/S to my TV using a vga cable, The option to only show the contents of my laptop on the external display, either through the shortcut Fn+F7(show only on external lcd display) or either through Windows 7 Right Click on desktop Screen resolution. If I try to show only on external display, my laptop screen turns off like its supposed to, however on the tv nothing shows up, a message in red appears "No Signal". This problem appeared after I installed windows 7 professional on my laptop, the problem was never there with Windows Vista Home premium. My laptop also has the necessary specs to run Windows 7, so I don't think thats the problem. However if I choose the options, Duplicate Displays, or Extended display, it works fine, but the inconvenience is that my laptop monitor stays on for 2, 3 hours while I am watching a movie.

System Specs:
Windows 7 Professional
Intel Core 2 Duo T5800@ 2.00 Ghz 2.00 Ghz
Installed Ram 4.00 GB (3.84 GB usable)
64 bit Operating System
Intel Graphics Media Accelerator Driver

Windows 7 Installed with a Clean Install with Vista Home Premium fully being deleted