A .001 file implies there are more files in the set (e.g., .7z.002 , .7z.003 , and so on).
To use this file, you cannot just open it by itself; you must have all the parts and "join" them back together. 1. Collect All Necessary Parts The Legend of Zelda BofTW.7z.001
Ensure every file has the exact same name except for the numbering at the end. 2. Extracting the Game Files The Legend of Zelda BofTW.7z.001
Go back to where you downloaded the file and ensure you have downloaded every numbered part. The Legend of Zelda BofTW.7z.001