I've gotten email from a bunch of people having trouble installing my D4 and D5 .DCU components.

These files ARE compiled in the proper version of Delphi. That's not the cause of the problem. It seems to be a problem with D4 (And D5), not with the components

Instead of using the "Component | Install Component" option, try this:

• From Component menu, choose Install Package.
• From the Packages Option screen, select the desired package (Typically User Components) then press the "EDIT" button. This will open up the package in the package editor.
• From the package editor, select "ADD", then find the desired .DCU file.
• After you press "OK" on the Add dialog, you will return to the Package Editor.
• Then press the "Compile" button. It should display a message that the component was added.
• When you close the Package Editor, be sure to select "Yes" when it asks if you want to save changes.

Let me know if the above procedure works or doesn't work for you. It's worked for several other people...