TV Loses signal when laptop closed- how to stop?

18 Oct 2002
North Wales
Hi all,
I have a HP Pavilion DV9605ea latop running vista 64 ultimate. I've connected this to my panasonic vierra plasma tv so I can surf etc and use the tv screen as the monitor. I've setup the nvidia control panel so that the laptop screen is cloned so it's displayed on the tv. The laptop resolution is changed to 1024x768 and all is well....except when I close the laptop lid, the display on the tv screen is lost.
I have my control panel power options set to 'do nothing' when lid is closed but the tv picture is still lost. This is driving me mad, any idea how I can close the laptop lid and keep the picture displayed on my tv?
The connection between the two is vga.
A quick response would be very much appreciated.
Thanks in advance,