What is an ICO file?
The ICO file format is an image file format used for icons in Microsoft Windows. It contains small bitmap images at multiple resolutions and sizes and an image mask to support transparency. Originally the icons had a size of 32x32 pixels square and used 16 colours. More recent versions of windows support icons at multiple sizes and colour depths. Current icon files hold images of typically 16x16, 32x32, and 48x48 pixels at 4, 8, and 32 bit colour depth.
Windows Icon Editor
is a Windows Icon Editor capable of editing ICO files.
ICO file format