Monitor ---> Laptop(sony vaio)

[sell high buy low]

ok so my desktop is becoming over run with bots and I need another computer to do school on.. I have this sony vaio and the backlight went out in it so the screen is so dim you have to practically sit in bright ass light and even then you can hardly see it.

My question is, when I plug my vga cable into vaio and then into my monitor, I power my vaio on, the monitor is on, then I hit Fn+ f7(switches screen to monitor), it does this then loads windows but then it switches off and has a green box that says No signal input, when I tryed another monitor its said No signal.. Help?Ive googled it and everything... Ive tried downloading drivers on the laptop,using different vga cables, everything i can think of..