ChemDraw: When I double click a CDX file the “Error sending the command to the program” message appears

Solution:

This error is very random and in most of the cases it will go away after your restart your computer. 

If you are using Windows 7, and the issue continues, please follow these steps: 

Make sure the file association is correct under Control Panel Default Programs Associate a file or protocol with a specific program.

1. Click Start and on the search box type “regedit”.

2. Right-click the “Regedit” option on the top and select “Run as Administrator” 

3. Go to \HKEY_CLASSES_ROOT\ChemDraw.Document.6.0\Shell\Open\ 

4. Click the File menu, and then click Export. Save the copy of the registry key on a known location in case we need to restore it later 

5. On that same screen double click the Command folder, right-click the Default Key on the right and select Edit or Change Data. 

6. Remove “/DDE” part of the command and click OK. Do not remove the “%1” section of the command line. 

7. Close the registry editor, restart the computer and test again. 
   
   If the issue continues, please try the following:

   1. Go to Control Panel Programs and Features Turn Windows features on or off.
   2. Remove the check mark from Microsoft .NET Framework 3.5. 
   3.Click Ok, restart the computer and test again.