1) Insert Disk 1 of Tiger Install Disk (you don't have to boot from it)
2) Double click DVD icon to open Finder window
3) Scroll down window till you find "Optional Installs" package.
4) Double click on this and follow install till you get to "Installation Type"
5) Select "Applications" and under it you'll find "X11"
6) Select it and follow the rest...

jchuzi