Black screen of death

Yesterday my daughter told me that she was having problems when rebooting my laptop [a Dell Inspiron 8500] - the screen was staying black.
I was expecting the worst; dead screen, hard disc failure or similar and went to have a look at it. However, when trying a reboot myself there was a flash of the windows Xp logo and the computer sounded as if it was booting properly.
Trying an extrenal monitor showed that the computer was working fine but the screen was still black.
I tried a google search and got a variety of suggestions, like completely reformatting the hard disc but it seemed unlikely that this would fix the problem when everything seemed fine with the external monitor.
Searching the Dell technical forums came up with the asnwer - they is a tiny plastic pin which senses if the laptop is open or closed, and this pin had stuck in the 'closed' position. The laptop thought it was shut! A few minutes of fiddling with a pin and voila! Screen working properly again.