Thinkpad T43 fn+f7 black laptop display - how to solve

[massits]

Hello to everybody
I have a problem to solve with my thinkpad t43, that is used by my son at the university.
He has pressed the fn+f47 but external monitor is blank.
Know anybody how to come back to use the t43 screen ?

we have tried to press fn+f7 again but the display remain black.

the t43 has a dual boot ( linux+WinXP ) all works, but win XP works for a while until the user log in, when the screen turns black.

pleas help us
thanks

[Neil]

The Fn+F7 switch cycles between three settings...LCD only, external only and external & internal LCD. If the internal LCD stays black in all three possitions, it means either the CCFL (back light) has gone out, maybe the lid switch is stuck or something else has interrupted power to the LCD (LCD inverter / motherboard fuse, etc.).

[massits]

thanks for your answer

The monitor works good becouse the problem is only on XP. In linux no problems.
before I read your answer I have tried to sturtup the laptop with a external monitor ( power on )
I have tried :
fn+f7 = only external monitor displayed / t43 monitor off
fn+f7 again = both monitors displayed
fn+f7 again = external monitor off / t43 monitor ok

the problem happens again if I restart the laptop.

what I have to do ?
thanks

[massits]

news
I have repeat the sequence but nothing new happens, every restart when XP runs, the screen go to black
with external monitor I have found that in settings/sistem there where 3 screens ( plug and play, generic etc.
I have tried to deactivate all excet the thinkpad screen.
At the first restart nopthing new, blank screen..
probably I'll reinstall the OS asap