It all depends on what distribution you want to run. Ubuntu is a Debian based distribution that is getting very popular. You can view the
download mirrors and download the latest installation CD image (named ubuntu-5.04-install-i386.iso). Burn it to CD and boot from it, that's how simple it is.
You may want to refer to the documentation (on the disc and on the website) and the
forums as well.
Ubuntu should work pretty well on a TP600 series laptop.
Håkan