How to unbind ALT in Lubuntu (LXDE)?

In Ubuntu when I hovered my mouse over VirtualBox and held the ALT key, it was sent to VirtualBox OS.

However, in Lubuntu (LXDE), when I hold the ALT key, it wants to switch between desktops and I can't use the ALT key inside VirtualBox.

How do I disable/unbind the ALT in LXDE, so it works in the VirtualBox window?

Unlike Gnome - the keybinding and mouse binding is controlled by a configuration file created when you first login - ~/.config/openbox/lubuntu-rc.xml

Open the file:

leafpad ~/.config/openbox/lubuntu-rc.xml

search for

<context name="Desktop">

Just below this are the statements highlighted:

Replace A-Up with A-S-Up and A-Down with A-S-Down

Alternatively just delete the lines below if you no longer want any ALT key mappings.

<mousebind>....</mousebind> 

You should be able to move between desktops with ALT+SHIFT and Clicking.

You will also note if you search for A-Up & A-Down there are various other similar mousebind XML tag situations where Alt and click are used - you could also think about changing these mappings to be consistent.

Save the file, logout and login to test the new key-mappings

#

! Disable Alt key

keycode 64 = NoSymbol NoSymbol NoSymbol NoSymbol

keycode 108 = NoSymbol NoSymbol NoSymbol NoSymbol

! Enable Alt key

!keycode 64 = Alt_L ISO_Next_Group Alt_L ISO_Next_Group

!keycode 108 = Alt_R ISO_Next_Group ISO_Level3_Shift

#

Save the above on a file eg:"disalt" and => xmodmap disalt