How do I get my dual display to work properly?

[ingeborgdot]

I have a toshiba tecra 8100.  It had been upgraded to xp when I bought it  used.  Anyway I have it connected to a projector that I use it for.  I have to go into it manually every time I want to have both my laptop monitor and pj going at the same time.  If I forget and don't switch the settings back my laptop screen is blank when I reboot.  Is there an easier way??????  What do I need to know????  Thanks.