You can run both at the same time by going on leave then switch user, click on launch then start new session.
This will put you at the login prompt, if you click on session (bottom left) you should be able to choose kde3.
Once logged in you can switch between the two using ctrl+alt+F7 or F8
You can run both at the same time. Remember that Linux is a multiuser system.
I have both running at the same time KDE3.5 for work and KDE4.0 for play and getting used to it.
Go to the KDE menu and select ‘switch user’ (you need to have registered multiple users in YaST) and select session KDE4.0 after that you can switch between KDE3.5 and KDE4.0 simply with: Ctrl+Alt+F7 and Ctrl+Alt+F8
Thanks for this. Feel abit daft now. Usu I guess I create a guest account which means I get a login screen at boot time, allowing me to select user and desktop. This time I just created my account (+root) and so I guess I get automatically logged into KDE4. I’ll have a visit to YAST to change this!