To open RAR files, you can use WinRAR, which is the software made by the company that invented RAR technology. To open .001 files, you need another program, such as HJSplit, 7-Zip or File Joiner.

Occasionally, you'll need to open several compressed files from one ZIP folder. While Windows does a fine job extracting, there are better tools to unzip.

You can open RAR files on your Mac computer with free apps like The Unarchiver. RAR is a compressed file format – similar to ZIP – that can hold many files in one place, and is especially ...