Many setup programs are 16-bit programs.
Use Regedt32 to navigate to:
If a file listed in KnownDLLs is missing from the %SystemRoot%\System32 folder, either extract it from the CD-ROM (expand), from your latest service pack (ServicePackFileName.exe /x), or copy it from another Windows NT that is running your service pack level.
NOTE: You may want to use Registry / Print Subtree to get a list of the KnownDLLs.
Sample: expand <CD-ROM:>\i386\system.dr_ %SystemRoot%\System32\system.drv
You MUST reboot your Windows NT computer.
NOTE: If you used the Windows NT CD-ROM, you MUST reapply your latest service pack.
NOTE: You should also verify that Wowexec.exe and Gdi.exe exists in the %SystemRoot%\System32 folder.