phantom1,....you might have a check in the box where it says "Hide extensions for know file types. Make sure it's unchecked so you can then delete/backspace out the 'txt' statement. It'll then go into a zip format automatically.
Do this: On the top of your computer,...go to Tools...then Folder Options....then View,.....and then scroll down to see if you have a check mark in the 'hide extensions' box. Remove the check mark and you'll be all set. Then remove the 'txt' wording.