To disable the right-click (context-menu) on the desktop,

you must go through the registry:

Click on the Start button. In the search field,

type the command "regedit" and press Enter.

Locate the following entry:

HKEY_CURRENT_USER> Software> Microsoft> Windows> CurrentVersion> Policies> Explorer.
Click on the Edit menu> New > DWORD Value > 32 bits.
Name it as "NoViewContextMenu" and double-click on it.
Enter 1 in the Value Data field. Click on OK.

Close the Registry Editor and restart your computer for the changes to take effect.

To restore this feature, you can simply delete the "NoViewContextMenu" 

or set its value to 0.