How do I change the monitor type in Debian to LCD internal 800x600 panel?
You don't necessarily need the "LCD internal 800x600 panel" option if you can find out the actual HorizSync and VertRefresh rates that equal this option. They are just two different ways to say the same thing.
Unfortunately, a quick google search only produced one result: http://www.mail-archive.com/linux-se.../msg02915.html
It seems that someone has got a working X configuration with 800x600 resolution for Toshiba 4030CDS on SUSE 6.1.
Anyway, it might be worth a try to run "dpkg-reconfigure xserver-xfree86" again, choose the "advanced" option and give the configuration program the same refresh rates which were used in that google search result: HorizSync 31.5-58 and VertRefresh 40-80.