I found a workaround for this issue.
I figured out that the checkmark "Disable Fences" in the control panel creates a REG_DWORD value 1 called "Disabled" in HKEY_CURRENT_USER\Software\Stardock\Fences. I loaded the registry hive for the default user and created the same "Disabled" value. I used the following instruction: http://support.microsoft.com/kb/146050.
Now when a new user logs to my computer, she does not see Fences welcome screen, but she can enable Fences in the control panel.