During the installation of ChemOffice Pro 3.5 for Windows, disk 2 is skipped, disk 3 is only used for a short time, and disk 4 is asked for twice.
Disks 1-3 mostly contain Microsoft's win32s. Win32s is required to run 32-bit applications under Windows 3.1 or 3.11, which are 16-bit operating systems. If your system already contains an equal or greater version of win32s than what is on the installer, disk 2 will be skipped and disk 3 will only be accessed for a short time. If you are running Windows 95 or NT, which are 32-bit operating systems, you will see the same behavior.
We are aware that disk 4 is asked for twice, as documented in the ChemOffice ReadMe. It will have no effect on the installation or how the programs work.