VSFLEX8.OCX contains the OLEDB/ADO version of the VSFlexGrid control. Because of that, it requires the ADO system DLL's in order to run (the same is True for the OLEDB controls that ship with VB6). To use VSFLEX8.OCX on a computer that only has VB4 or VB5 installed, you will need to install the ADO system DLL's.
If you are not using OLEDB/ADO, consider using the VSFLEX8L.OCX version of the control, which is not subject to this limitation.