Can't gain access to your game as I don't have WinRar, but if it's an EXE (or has any additional files) then you might want to take a look at the Clickteam Patch Maker:
http://www.clickteam.com/eng/patchmaker.php
The Freeware version is exactly the same as the full version, except for an advert for Clikteam at the end. Just specify the folder on your computer where the first version is, the folder where the new version is and let the program build the patch for you.
Hope this helps.
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