Thanks to Vincent Batts for providing KDE 4 packages which can co-exist with KDE 3.5.x, i am now running KDE 4.1.0 on my desktop at my office (i didn't use this desktop as much as my desktop at home, so i used it for testing this KDE 4 packages). All i did was install all the kde and deps packages except for poppler which was provided by Slackware and it has newer version than Vincent's package.
Next thing is running xwmconfig to switch to KDE4. After than, i ran startx and voila..... huh? Stil running KDE 3.5.9? Hm... so the script at .xinitrc didn't work at all. So i checked the script and i looked at the QT4DIR and KDE4DIR environment variables. They didn't exists on my system, so i tried to use this command to initiate it
i only need to do this, as the script in .xinitrc will find the the variables and load it with the correct KDE 4 packages. So far, everything works normally, except for some specific configuration i have made to KDE 3.5.9 which is temporarily gone (i may have to re-add it again in KDE 4). I also lost my previous konsole settings which display my username, hostname, and current working directory. The default setting in Terminal just displays the bash and bash version. Luckily, a simple script on .bashrc would do the tricks
One thing that bothers me is that when i looked at Control Center, it still displayed the old version of KDE (Look at the screenshot below)