The problem was in the name of the macro $(ProjDir). In Visual C++ 2010 it's $(ProjectDir)
$(ProjDir) -> $(Proj ect Dir)
Some macros altered their names (after so many years)!
The command copy \PDFXChange\dll.Debug*.* C:tests\ocx2010\Debug should copy some DLLs into the folder where the next command regsvr32 /s /c "C:tests\ocx2010.\Debug\LayoutBox.dll tried to register the target file. It couldn't find any DLLs there, so it quit with the error message.