Installation instructions for the ThinkPad X40
Here is a tutorial (in german) for installing Gentoo Linux on a IBM Thinkpad X40.
Of particular interest my be the patches section, where I collext my patches for the X40. Currently there's a patch for Linux 2.6.9 which adds Speedstep support (a backport of the 2.6.10-mm patch).
Here are general configuration information for installing and configuring Linux on a X40