You have to use any 7z Compatible program to open the file the latest WinRAR can open them and ToD. when i make mods that use the 7z compression i use a tool that makes the 7z's in an SFX (Self Extracting Executable) so the program takes up a few KB's and is built into the 7z file with no tools required to extract it. (Like what i done with GTA MM (Most Modded) 1.0B i got the newer version smaller than the first)