TV won't recognise computer connection.

[Alice456]

[strike]Edit: Apologies, this is the wrong category, my computer is a PC, not a laptop. Nevermind
[/strike]
I tried both a vga and hdmi cable and neither would work, its not the ports as on my computer as i was able to connect it to another monitor, and not on my tv either as I have my xbox and another computer connected to it(which worked with both the vga and hdmi).
is it possible that my tv and computer aren't compatible?

 

[Marrobot]

What happens when you do plug it in, does the tv think that there is nothing or does it look like it gets signal but the screen stays black?
[strike]On your laptop, go to 'settings -> system -> monitor' and see if windows is configured to only output to the build-in monitor.[/strike]