If you make a text file named Template.txt in the folder C:\Windows\ShellNew whatever is in that file will be included in new text files created as you describe.
I forgot this part. For this key
HKEY_CLASSES_ROOT\.txt\ShellNew
Filename value of type REG_SZ should be
Template.txt
Edit: I guess using the filename "Template.ext" is only a convention. It doesn't trigger the entry. Whatever filename you use must be specified per extension in HKCR.
Edit2: That's what happens when I try to take a shortcut. Thought I knew that one so I didn't search.
I should have gotten it right the first time but because the file name used was "template" I somehow got the idea that file in that folder did it all. The memory isn't as good these days. Glad it's working.