Open your registry and find the key below. 

Create a new DWORD value named "NoActiveDesktop", and set the new value to equal "1" to enable the restriction or "0" to disable the restriction. 

Note: This restriction can be used either on a user by user basis by adding it to HKEY_CURRENT_USER or on a computer wide basis by adding it to HKEY_LOCAL_MACHINE. 

Key:[HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Policies\Explorer]
Value Name: NoActiveDesktop
Data Type: REG_DWORD
Data:(0 = disable restriction, 1 = enable restriction) 

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