Built-in LCD display on DualScan PowerBook G3

[Ian]

Hello.

I have YDL 2.2 on my PowerBook G3 with a Dual Scan display. However, when I
installed YDL, I also had an external monitor attached (I didn't use my
built-in display at the time). But now that I don't have that monitor
attached any more, I can't seem to SEE YDL! It boots up, I'm sure, but it
doesn't display anything! So, my questions is this: how can I tell YDL to
use my dual scan display??

Thanks!

- Ian