Welcome to the old DLL Hell <g>. This is in Visual Basic, not in SetupBuilder. You have to find out (in your VB program) what kind of incompatibility issue it has (if any!) with newer versions of MSCOMCTL.OCX. Note: most MSCOMCTL.OCX errors are related to a missing, corrupt, or unregistered MSCOMCTL component.

BTW, you can install a downgraded version by setting the replacement option in SetupBuilder to "Always". But of course, this will only work if the file to be replaced is not protected by Windows. Windows File Protection (WFP) prevents programs from replacing critical Windows system files. Programs must not overwrite these files because they are used by the operating system and by other programs. Protecting these files prevents problems with programs and the operating system.

If the file is not protected by WFP and you downgrade the existing .OCX then it is very well possible that existing applications stop working. That's why you should never downgrade existing components.