Every distro does it differently, so which one are you using? If it's Mandrake 9.1 like it says in your info, then..
How do you login? Via "startx" or do you use a gui? If a gui, then in the drop down menu, select the wm of your choice. If via startx, then you can either setup a .xinitrc in your home directory, OR the easier way might be to just run:
kdm (as root)
login as the user, select the wm of your choice and then logout. There are other ways, but for extreme n00bs that's probably one of the easiest options.