Trying to connect Laptop to PC...

I'm trying to hook my Dell Inspiron 1750 up to my Sony Bravia TV (this seems to be a common theme). It was working fine before using the mobility centre, or the Fn (function button) above F1. For some reason now whenever I try to use either of these it tells me there is "No External Display Is Attached", believe me there is. I am using a VGA to HDMI cable as the Dell does only has VGA.

A lot of sites tell me to go to the Display Driver settings and force the PC to detect the external monitor, but this does not appear possible on my PC. A lot of sites mention NVidia, but I appear to have an ATI Mobility Radeon?...I think, and there are no settings that I can find for this. I tried finding the device in Control Panel but there is nothing useful. I've literally tried everything, except kicking it. (While this might make me feel momentarily better, the lasting effects might not help my cause.

I have the correct input setting on the T.V and have tested the port works OK with my SKY box. I've tried unplugging everything and turning everything off and on again, (and all that jazz). I've tried messing about with the display settings, tried identifying monitors and, basically pressed all the buttons that seemed relevant.

Can anyone help?!