FYI: While looking for clean install of 5.5, my Samsung 19" monitor worked on Gnome but not XFCE. The Samsung worked for the bootup splash screen but expanded vertically when the application graphics started. This prevented install or login because the widgets were not visible. However, I could do the install with a generic 17" monitor on my Zotac ION330 which has integrated Nvidia.
I noticed that Gnome had a Nvidia splashscreen but XFCE did not so I installed nvidia-settings and rebooted with the Samsung connected. Now it works.
BTW, I suggest to use a recently daily ISO because release 5.5 (which probably should be deprecated) has 380 updates.

