IP (IconPackage Theme File)
The IP Data file format
Files with the IP extension are most commonly associated with IconPackager, a program that created desktop themes for Windows computers. IP files are collections of icons used for such themes. The file can contain various amount of icons. IconPackager can then use them to replace the default Windows icons with them.
Technical details of IP files
IP files are compressed collections of icons. They are compressed using the common and widely supported Zip compression. Thus, they can also be opened by archive programs such as 7-Zip. The compressed file can contain, as stated above, a number of icons in the ICO format, as well as icon libraries (ICL) and the ICONPACKAGE file used to execute or save the theme.