Right-click AJArchive.7z > Select 7-Zip > Select "Extract Here" (to keep files in the same location) or "Extract to [Folder Name]" .
If 7-Zip displays a "cannot open file as archive" error, the file may be corrupted. AJArchive.7z
Try opening the archive using WinRAR, which sometimes handles corrupted headers better. Right-click AJArchive