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.
Value Name: NoActiveDesktop
Data Type: REG_DWORD
Data:(0 = disable restriction, 1 = enable restriction)