Can't create controls on an MDI form

Important Notice

The pages on this site contain documentation for very old MS-DOS software, purely for historical purposes. If you're looking for up-to-date documentation, particularly for programming, you should not rely on the information found here, as it will be woefully out of date.

■ You tried to place a Toolbox control and a form whose
  FormType property is set to 1 - MDI. Only menu controls
  can be placed on an MDI form.
 
■ If you need additional help, move the cursor to a keyword
  and press F1 to open the Help window.