I just installed Xubuntu 12.04 on my new machine a ThinkPad a22p 12 years old (or maybe more) with a 16bits 800x600 screen.
I see the video "duplicated". I managed to solve the problem with the life version running on a CD by using the argument VGA=788, but in the installed version I do not manage to get solved.
This is what I done with no success:
Edit the boot parameters in /etc/default/grub
I also added a line VGA=788
I edited the grub command at boot adding vga=788
thanks for help!