What is .PACK file?
File used by CustoPack Tools, a program used for customizing the Mac theme; contains theme visual styles, sounds, and graphics for Mac 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.
Recommended Software Programs to open .PACK file