[newbie] Switchdesk

[The BOFH]

When I installed MDK 7.2 a month or so ago, it came up in Gnome.  I swear 
that at that point I used switchdesk to change to KDE.  Now I'd like to 
play with Gnome some more but I cannot find it on the system anywhere.

I've persused the list archives, and found some messages indicating that I 
should create a .Xclients file, which I did, but startx still brings me up 
in KDE.

Do I also need to modify some other file?  Was switchdesk truly removed by 
some upgrade I did along the way?

Thanks,

S