Cannot connect my Vaio TX5XN to a Dell monitor

Hi,
When i connected my vaio to the lcd dell monitor vai vga (which is only about 3 yrs old and works perfectly), nothing happend. Screen is cracked on the vaio so i can only see half the screen. I have tried everything like using the windows mobility centre, and fiddling with the display settings but i still get nothing. Oh and Fn+F7 doesnt do much apart from give you two options “lcd only” and “setup”, lcd only does nothing and setup gives me a window with one checkbox…..rubbish.

Sony Vaio pcg-4k!m
with vista

if anyone can help mucho kudos..