Introduction
When creating icons for Windows applications, sometimes you can't just use
a .png file and you must use a special .ico format.
The ICO format is
a collection of .png or .bmp images in a special structure.
Fortunately, there are readily available tools to help you take a simple .png
and convert it to the .ico file. This guide will look at a couple options.
Inedo Icon Maker
The Inedo Icon Maker
software can be downloaded from the GitHub releases as a .zip file.
Unzip the file to get IconMaker.exe standalone file.
Run it, and drag your image file in to the window.
It accepts up to 256x256 pixel images.
Note that it may ask you to install some .NET framework prerequisites and that is expected.
Download the latest release on GitHub.
Icoconvert.com
If you don't want to or can't download and execute the Inedo Icon Maker .exe file,
you can use a free online service like Icoconvert.com.
Icoconvert.com allows you to upload an image and get a .ico file back.
Conclusion
After following this guide you should be able to convert a .png file up to 256x256
to a Windows .ico format that you can use as an application icon.