One of my customers is getting the following error while trying to install one of our applications:

The application or DLL C:\WINNT\System32\Comdlg32.ocx is not a valid Windows image. Please check this against your installation diskette.

The message above is within a dialog box from the Visual Basic Setup toolkit: Setup1.exe

Does anybody have any idea what the cause of this may be? Any suggestions would be greatly appreciated.