AJG, sort of off topic but ...

In debian systems the links to gdm, kdm, or xdm from /etc/init.d are in all rcX.d directories, do the following...
ls /etc/rc?.d/*gdm
it will show something like this:
/etc/rc0.d/K01gdm /etc/rc2.d/S99gdm /etc/rc4.d/S99gdm /etc/rc6.d/K01gdm
/etc/rc1.d/K01gdm /etc/rc3.d/S99gdm /etc/rc5.d/S99gdm

So what runlevel did you select to startup?
Let's assume you chose runlevel 3, and using my above system setup where I use gdm, so then either:
chmod a-x /etc/rc3.d/S99gdm # to make the entry non-executable
or
rm /etc/rc3.d/S99gdm # to delete the link

then when you boot up you won't have gdm started in runlevel 3

HTH

~rock