Textpad - Open new files in same instance by default

I've been a TextPad user for years, and when you install it, it adds an item to the context menu in explorer called "TextPad" that will open any file with textpad, regardless of the extension (whether or not its readable is another matter of course). Now, I could be remembering wrong, but I recall on older computers, if you opened a file with this method, it would open any such files in the already-running instance of TextPad. Now, when I do this, it seems to open a new copy of TextPad every time I open a new file. I'd perfer it to use the same instance. How can I enable this behavior?

There is an option in TextPad to only allow one instance to run:

Configure > Preferences > General > [ ] Allow multiple instances to run

Uncheck that box and click OK.

Now when opening any file in Textpad it will use the same instance.

• Open Textpad, go to Configure in the menu then Preferences.

• Context Menu is checked for some strange reason. Uncheck the box and then close the interface.

• Open Textpad again and check the same box.

• Now it's in the context menu for all files.

It must fail in Windows 7 upon the original install.