Many sites allow you to download free ICO files, but you may prefer to create your own as well. Do this by painting an image using a graphics program, saving the file as a Bitmap and then converting it into an ICO. You need special software to do that, but you can find it on the Web. Once you have an ICO, you can use as a folder icon, embed it in applications you build or turn it into a favicon that appears in a browser's Address bar when users visit your web site. Many computer users create ICOs as stand-alone files because they have no need to use other methods.
You may toss trash into them daily and drag them across your desktop, but you may not know what icons really are. These tiny images, found on folders, toolbars and browsers, can exist as individual ICO files or inside files known as DLLs. Your computer can work with icons regardless of their origin. Some icons are ICOs and others are not because icon creators choose to distribute them in different ways.
Dynamic Link Libraries live all over your computer. Find them in your Windows directory and in the folders of applications you install. A DLL, which is a single file, can contain programming logic and important information. DLLs are useful because different applications can share a single DLL and use its contents. You might never download DLLs, but they still wind up on your computer because installation programs may put them there. You cannot make a DLL run by double-clicking it. Applications, however, can access a DLL's information programmatically.
DLLs as Image Libraries
The Shell32.dll file, found in your Windows directory, holds components that help keep Windows running. This file is also home to many of the icons that you see in Windows. Right-click a folder, for instance, and you can access the Properties window that allows you to change the folder's icon. When you click that window's "Change Icon" button, you will see all the icons that exist in the SHELL32.dll file. Double-click an icon to apply it to a folder or simply browse through the collection to see the variety of free icons that exist on your computer.
Some applications may include ICO files in their download packages. If so, you can search for ICO files in the application's folder and copy them if you'd like to use them elsewhere. Other applications may hide their icons inside DLL files similar to Shell32.dll. You can't view the icons inside one of these DLLS by double-clicking it, but you can download special software that can extract those images. If you would like to share your icons with others, you may want to send them ICO files. Otherwise, they will need special software as well to view icons residing in DLL files.