xdm compliant with gnome?

[Yao Wang <ywangz eecs umich edu>]

Hi:

I am having some trouble with putting gnome to work in RH6. If I log in as
user at the login window and try this on the xterm: (press F1 after
passwd) 

panel &
[1] 5295
gmc &
[2] 5305 
** WARNING **: Root window clicks will not work as no GNOME-compliant
window manager could be found!
exec gnome-wm

Gnome loads up but with a warning message as above. However, this seems to
be the trouble that kicks out user after pressing enter with passwd. I
noticed the gdm in /usr/X11/bin/ however. as I change the xdm to gdm in
the following line:
x:5:respawn:/usr/bin/X11/xdm -nodaemon
no window can pop up with an error message like:
window spawning too fast, halt for 5 minutes (whatever)

I have not found anything helpful in the FAQs, could someone kindly give
me some help? 
1.) what is the gdm for?
2.) how to I load gnome properly, I put those three lines in .xinitrc and
apparently they kicked me out while logging in.

Thanks a lot

yao