Originally Posted by Josh Keller
How are you changing it to a .zip file?
Step 1)Click "Start" and select "Control Panel." Next, double-click "Folder Options." From there, choose the "View" tab.
Step 2) Un-check "Hide Extensions for Known File Types" and click "OK."
Step 3) Navigate to the file whose extension you would like to change. Right-click the filename and select "Rename."
Step 4) Type a new filename. The extension is the portion of the filename that follows the period. In the accompanying image, the extension was changed from "txt" to "zip" Press "Enter"; you will be asked if you are sure you want to change the filename. Select "Yes."