firstly you'll need a linux bootdisk, if you didnt make one during installl good on you
just toddle off to google and search for tmsrtbt.
Boot off this floppy and mount you /dev/(linux partition)
bounce into /etc/inittab and your are looking for a line something like this
i think for gui login its something like 5?, not too sure though but for a command login it should be 3 as above
or as the guy above me said