Hi Clifford, thanks for your reply and welcome!
I dont think its a faulty switch as it was working fine yesterday under Windows XP.
My graphics card is ATI Mobility Radeon X1300 and my notebook is a Dell Inspiron 6400. I downloaded the Windows 7 drivers for it after installing Windows 7 RC yesterday,
Under the power options, it only gives the options to sleep, hibernate, turn off or do nothing when I close the lid. At the moment that is set to 'do nothing'. I dont want it to shut down, hibernate or sleep as sometimes I leave my laptop on downloading or running tasks. With Windows XP, when this was set to 'do nothing', the screen would still turn off.
I've seen a number of users having the same issue as me on other forums but nobody has yet been able to solve it!