hi
edit your /etc/inittab file and change default runlevel to 5
Code:
# The default runlevel.
id:5:initdefault:
and delete the S99gdm file from /etc/rc2.d directory
now , when you boot up write a "2" after the kernel name in the boot loader prompt , i think you use grub ,and unfortunatelly i don't know grub , i think you need use the grubs console but i'm not sure.
if you installed the driver from source you can uninstall it with "make uninstall" command , but if you installed it from package use apt for remove