Occasionally something strange happens and the computer tells the .ZIP file to open elsewhere.
Right click on the .ZIP
In the following window click the "General tab" ( if not already selected )
Then click "Change"
You will then be given a selection of programs to choose from ( Depending on what programs you have installed )
Select "Windows Explorer Microsoft Corporation" then "OK"
Make sure "Always use the selected program to open this kind of file" box is checked with a tick, it should automatically be checked.
Click "OK" and you're done.
This applies to ALL .ZIP files, you will not have to do this more then once.