File used by CustoPack Tools, a program used for customizing the Windows theme; contains theme visual styles, sounds, and graphics for Windows icons and the desktop background; can be downloaded from the CustoPack Tools website.
CustoPack Tools themes are distributed as self-installing .EXE files. The PACK file for the theme is contained within the EXE file, so users rarely ever see the actual PACK file. If you would like to access the PACK file, use a program like 7-Zip to open the contents of the EXE file.
File created by Pack200, a utility included in Java 1.5.0 that compresses .JAR files; contains a JAR file that has been compressed by up to sixty percent; used by Java Web Start clients to retrieve and unpack JAR files for Java programs.
PACK files are often compressed into .PACK.GZ files. They may also be seen with the compound ".jar.pack" extension.