If the wide taskbar is obstructing the apply button then drag the properties window up a bit. To make the taskbar narrower then untick the 'lock the taskbar' first then use pointer to narrow it then lock the taskbar again. If auto hide still isn't working after applying 'hide the taskbar' then it could be an icon in the notification area that is always(wrongly) sending an alert. Similar as when you receive an email alert or security alert that will auto show the hidden taskbar.
For some reason, you can't drag the window 'off screen' a lot like I could on my PC.
The window has to stay within the confines of the screen area which is really annoying.
Also the option 'auto-hide the taskbar' doesn't work as I can't apply the changes (as the taskbar gets in the way of the Apply button)) and closing down the settings window means that nothing has changed as the changes don't get applied on exit.
I think I remember seeing an icon in the notification area of the taskbar about making backups of her data.
Perhaps if this notification is switched off, I may be able to apply the changes.