Help!

Okay. I'm a newbie running an old Pentium III laptop. It's a Sharp PC-MV10 series. I'm new to Ubuntu (actually, it's Xubuntu with the Gnome desktop) and so far I'm loving it. However, I have a big problem. I can only use it with an external monitor plugged in. For some reason, it won't address the laptop's internal screen. During boot the Xubuntu sign-on screen mirrors on both screens...but that's it. Once booted, it refuses to see the laptop screen. 

This is the chip set:

Intel Corporation 82830 CGC [Chipset Graphics Controller] (rev 04)

I've tried various applications and resolutions, to no avail. Ubuntu just refuses to use the laptop screen. XP works fine on both, so it's not hardware. Warning though--a friend who's a Linux expert messed around with this for hours and finally gave up.

Anyway, if anyone has an idea, I'm all ears. Thanks in advance.

Here's xrandr output:

Screen 0: minimum 320 x 200, current 1024 x 768, maximum 1024 x 1024
VGA connected 1024x768+0+0 (normal left inverted right x axis y axis) 304mm x 228mm
1024x768 75.0*+ 75.1 75.0* 70.1 60.0
832x624 74.6
800x600 72.2 75.0 60.3 56.2
640x480 75.0 72.8 72.8 75.0 66.7 60.0 59.9
720x400 70.1
TMDS disconnected (normal left inverted right x axis y axis)

ls /etc/X11
app-defaults X xorg.conf.failsafe Xsession.options
cursors xinit Xresources XvMCConfig
default-display-manager xkb Xsession Xwrapper.config
fonts xorg.conf Xsession.d

cat /etc/X11/xorg.conf
# xorg.conf (X.Org X Window System server configuration file)
#
# This file was generated by dexconf, the Debian X Configuration tool, using
# values from the debconf database.
#
# Edit this file with caution, and see the xorg.conf manual page.
# (Type "man xorg.conf" at the shell prompt.)
#
# This file is automatically updated on xserver-xorg package upgrades *only*
# if it has not been modified since the last upgrade of the xserver-xorg
# package.
#
# Note that some configuration settings that could be done previously
# in this file, now are automatically configured by the server and settings
# here are ignored.
#
# If you have edited this file but would like it to be automatically updated
# again, run the following command:
# sudo dpkg-reconfigure -phigh xserver-xorg

Section "Device"
Identifier "Configured Video Device"
EndSection

Section "Monitor"
Identifier "Configured Monitor"
EndSection

Section "Screen"
Identifier "Default Screen"
Monitor "Configured Monitor"
Device "Configured Video Device"
EndSection