I have manually installed XFCE, and don't quite like it. Also I have a problem which I think is related to the newly installed DE. When I downloaded Chrome from google and tried to install it by clicking on the .rpm, I always get an error "failed to install, query invalid". I then right clicked the file and found the default install application is "apper installer", which also had a gnome like GUI. If I choose "install/uninstall software" instead, I can install the .rpm normally. Besides, some application icons changed which I don't know if it's XFCE's fault.

All in all, I'm now trying to remove XFCE. But "zypper rm xfce" would result in "can't find pkg xfce". In YAST, I couldn't figure out how to "delete" XFCE. There is only "not install" option when right click on XFCE.