Why can't I make my Projector my primary monitor on my X61?

[epu]

When I plug my projector (NEC VT491, great piece!) into my X31, the laptop LCD would automatically shut itself off on restart and make the Projector the primary monitor.

This doesn't happen on my X61.

#1 - It allows me to make the projector my SECONDARY monitor and drag stuff across to it.
#2 - If I try to make the projector my primary monitor, it immediately disables itself and doesn't give me the option to make it a primary monitor.

Am I doing something wrong here? No, I didn't install the drivers. Then again, why should I have to? My X31 is running XP SP1 with no patches or hotfixes. My X61 IS running SP2, but I don't see what the problem is.

Neither the standard Windows Control Panel OR Lenovo's Thinkvantage software is of any help . . . .

Thanks in advance for your help.