Microsoft Word restores all open documents when clicking on a .DOC file
You can fix this problem by blocking Word from using DDE to open files.
In the HKEY_CLASSES_ROOT\Word.Document.12\shell\Open
key:
- Delete or rename the
ddeexec
sub-key
In the HKEY_CLASSES_ROOT\Word.Document.12\shell\Open\command
key:
- Delete or rename the
command
value (not to be confused with the command key.) - Edit the (Default) value and add
"%1"
(including quotes) at the end
This solves the problem for .docx
files. If you also want to solve it for .doc
files, do the same thing for Word.Document.8
Thanks to: Rafael's Within Windows which has detailed instructions.