Solution:

Delphi 4.0 seems to have stricter parameter data type examination. We found the program will work after the modification as follows: In Procedure TfrmInit.butChangDevClick(Sender: TObject); Original ---> {Select devcie from device list} lErrCde := DRV_SelectDevice( frmInit.Handle, 0, lDeviceNumber, szDeviceName[0]); Modify to ---> {Select devcie from device list} lErrCde := DRV_SelectDevice( frmInit.Handle, False, lDeviceNumber, @szDeviceName[0]); In Procedure TfrmConverting.FormClose(Sender: TObject; var Action: TCloseAction); Original ---> var i : integer; Modify to ---> var i : Longword;