Change Desktop Environment without Admin Access
I'm wondering if anyone can tell me how I might switch my desktop environment on a workstation that I do not have admin access on. The machine is running Redhat Enterprise Desktop v3 and there are a few alternative desktop environments I can choose at the login screen, but I would prefer to use Gnome or KDE. I'm fairly certain Gnome is already installed on these machines, as I've seen other users using it. There are also some directories present in my home directory like .gnome, .gnome2, .gnome3 so I have a feeling it is on the machine, I just don't know what file(s) I need to edit so that I can use it. Any suggestions?
P.S. Sorry I know this question gets asked a lot, but after searching the forums and all over Google I can't find a response that fits my situation!