Screen not working but other monitor work

Your "F"keys are multi function. Look for the one with a picture of a monitor. Press the FN key adt the appropriate F key at the same time. You are probably in remote monitor mode. The F key is usually F5 or F8.

I have a similar problem with my Sony notebook VGN-SZ430N. The problem started after I upgraded OS from Vista to Windows 7. At some point the screen worked fine, but after fixing other problems and loading drivers my screen went blank after one of the reboots. More exactly it shows the beginning of the boot but then the screen goes black before playing "Windows" tune. I can see shadows of correct images on the screen, and I can even operate the laptop by shining a flashlight onto the screen. I tried Fn-F5, Fn-F6 and Fn-everything else. Nothing worked. At some point I restored the registery to the previous configuration and the screen started working again, but after I updated required drivers for other devices, the problem reemerged. I can restart my computer in safe mode, and the screen is working fine, but subsequent normal boot makes the screen dark without backlight but with the image present.
I still don't know how to fix the problem

To me it sounds like: 1)Your LCD is broken. Or 2)Your LCD is not connected Or 3)You have disabled the display. Go into your graphics control panel (i don't know what graphics card/integrated graphics card you have...) and for the display option select :Laptop Display" or something like that. You usually can cycle through them using one of the Fn+F7(or F8...etc) combinations.