How to clean xdm at startup ?

I tried tne new version of xorg and I had some problem when I reboot.Xdm start and freeze because I had dome problem whith my xorg configuration.To avoid xdm automatic launch, I just do : emerge -C xdm.After it's easy to re-install.

Note : You can startup grub in single mode by adding "single" at the enf of the boot line (e to edit).