how to disable desktop background (permanently) in xfce 4.6.1

[Globe Trotter]

I have been using Xfce 4.6.1 and I was wondering how to disable the desktop background completely. Previously, there was a button in the Desktop in the Xfce Settings Manager (saying "Allow Xfce to manage the desktop") but that seems to be absent in the XFCE 4.6.1 Fedora 11 installation I am using.

Any suggestions? 

While we are at it, I wonder how I can make the fonts use the system default in the "Appearance" menu. is it by leaving the DPI setting unchecked in the Appearance -> Fonts tab?

many thanks for any help!

Best wishes,
T