Excerpts from my XF86Config :

Section "Device"
Identifier "Videocard0"
Driver "trident"
VendorName "Videocard vendor"
BoardName "Trident CyberBlade/Ai1"
Option "intern_disp"
Option "extern_disp"
Option "xinerama"
Option "Display" "Dual"
#Option "crt_screen"

The problem I have is that if I boot up connected with external projector
and then use Fn+F7 (my laptop is an IBM TP i1300), everything is fine.

If not, no amount of post boot Fn+F7 pressing puts any signal through. I
have lived with this situation for months now but at a recent conference,
this was rather annoying.

How do I fix this problem ?