I had a 'Home' partition and 2 other partiton, initially i had installed a gnome distro(Linux mint 11-64 bit). consider the following situations. 
1. Instaling a KDE distro by formating the gnome distro partition and reuse the existing 'Home' partition. 
2. Installing KDE full desktop in Linux mint gnome version. (changing the desktop environment to KDE in a linux with gnome desktop)
3. Sharing the  'Home' partition of the existing 'gnome'/any other linux with a new KDE Distro.
In all the case  the after login Konsole will appear. No normal desktop appears.
Note: all distros have the same user name. and are 64 bit versions.

I feel some files and folders are kept in a common place instead of a specific folder like 'kde' folder or any 'other desktop environment' folder in th home partition. atleast while log in time kde should detect the gnome/other desktop files.

Reproducible: Always

Steps to Reproduce:
1. Installed  a Linux mint with gnome desktop
2. Installed KDE desktop from package manager or installed another distro(linux mint KDE) with KDE desktop. in both cases Home with data is the same(with out formating).
3. restarting the system and log in.
Actual Results:  
Only konsole window available and appeared

Expected Results:  
Normal KDE desktop should be shown.

There should be provision to permanently mount other linux partitions in different names with password authentification. not exactly the same way as windows do with their partition. Linux is not flexible in this case, restrict mounting to the predetermined mount points.