You can either directly hack the registry, or there’s a freeware utility that adds the functionality back… we’ll show you how to do both methods.
Using the Registry Hack Method
Open up regedit.exe through the start menu search or run box, and then browse down to the following key:
Double-click on the (Default) key to open it up, and then replace the path for notepad with the full path for your preferred editor, making sure to leave a space and then the %1 at the end (which inserts the current file name into the path)
Using the Easy Method
Using the freeware and open-source Types utility, you can easily change file types… just find the “bat” extension in the list, or filter by the “batfile” class, then open up the properties. You can easily replace the editor by just using the yellow icon next to the drop-down and choosing your preferred editor.
Of course, you can use this application to change the default editor for any file type, not just batch files.
Download Types from sourceforge.net