Old version of 7-Zip (before version 15.06) used file sorting 'by type' ('by extension'). New versions of 7-Zip (starting from version 15.06) use another file sorting Why 7z archives created by new version of 7-Zip can be larger than archives created by old version of 7-Zip?
Then you can change file associations and some other options.
Right-click the icon of 7-Zip File Manager, and then click Run as administrator. You must run 7-Zip File Manager in administrator mode. How can I set file associations to 7-Zip in Windows 7 and Windows Vista? User FAQ Can I use 7-Zip in a commercial organization?