Ad: This forum contains affiliate links to products on Amazon and eBay. More information in Terms and rules
I always resize in Picture manager and save to a secondary folder within the folder that has the original pics, so I keep the originals as is.
Just use MS Paint people. It is already installed on your computer, very easy to use, and only takes a few seconds.
I really don't understand why people have such a problem with this, and keep searching for "programs" to do so.
Use MS Paint!