Thinclient, Installing linux without graphical interface: KDE or GNOME

Small guide and question.

Guys, my question is fairly simple, and I'm able to do it with an old fedora (5 if I'm not mistaken) version, but I want to be able to do it with latest linux distros.

The purpose of this project is to boot rdesktop directly (to make the machine a thinclient), and here's how I do it at the moment:

0) Install fedora removing any graphical interface such as KDE or GNOME, but leave X11 option marked
After installation:
1) vi /etc/rc.d/rc.local -> add: startx
And then:
2) vi /etc/X11/xinit/xinitrc -> add somewhere in the middle: rdesktop -a 16 -f 192.168.x.x
Done.

It works because I removed KDE or GNOME when installing fedora.

BUT, my question is, is there a way to remove kde or gnome from booting? (and booting with only the basic X11).

For instance, say I wanna do this with Ubuntu 9.10, how to I remove gnome?

Thanks in advance.