I'm trying to open a Microsoft help file, but ChemDraw keeps trying to open it and can't.
The Microsoft help file you are trying to open is probably a .CHM file. This is the old extension ChemDraw used to use in versions previous to 4.0 as the default ChemDraw format. Microsoft has decided to use the same extension for compiled help files. We have no control over other companies using the same extensions.
An extension can only be assigned to one application or another. ChemDraw 5.0 and below will always reassign the .CHM extension to ChemDraw each time you launch ChemDraw. The latest version of ChemDraw will not do this. You have two options:
1. Upgrade to the latest version of ChemDraw.
2. Otherwise, if you want to open the help file using Microsoft's application rather then ChemDraw, drag the .CHM help file you are trying to open onto the HH.exe icon. This will open it up properly. If you are unsure where the HH.exe application resides, do a Find File on your hard drive for it. Typically, it is located in the Windows folder.