Error 0x80040101

Value: -2147221247 | 0x80040101 | 2147746049

What does it mean ?

DRAGDROP_E_ALREADYREGISTERED  
This window has already been registered as a drop target
Value: 257 | 0x0101 | 0b0000000100000001

Where does it come from ?

FACILITY_ITF  
COM/OLE Interface management. FACILITY_ITF is designated for user-defined error codes returned from interface methods
Value: 4 | 0x004 | 0b00000100

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Other Errors for FACILITY_ITF