The program tpdualscan for IBM thinkpad notebook computers prevents the ghost or mirror effect on X11 where graphics (windows etc., and cursor) appear on two positions on the screen. It should be started along with the X11 server. The .xinitrc may be a good place to call tpdualscan.
This version of tpdualscan.c was picked up from:
http://www.lares.dti.ne.jp/~aikawa/linux/360/tplinux.html
Here is a binary version of tpdualscan,
compiled with gcc 2.7.2.3 on kernel 2.0.34
using libc.so.6 and ld-linux.so.2
on 12 November 1999.
Don't forget to do chmod 4755 tpdualscan
to allow a regular user to tweak the graphics device
during startx/xinit.
gcc -O2 -o tpdualscan tpdualscan.c chmod 4755 tpdualscan