Good to hear you trashed your system, keep doing it.
I trashed mine yesterday playing around. Recovered it in about 5 minutes with clonezilla.
Desktop settings for all users are in a hidden dot file .kde4. Always keep a backup of .kde4.
New system, old /home directories?
As root in a terminal:
chown -R user1:user1 /home/user1
chown -R user2:user2 /home/user2
If partitions need reattaching use the PCC Contol Centre (make sure you do not have two different /home directories)
If the install is doing odd things do you have a good install?