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.

How to Combine RAR Files in WinRAR. The RAR format optionally splits large files into several compressed parts. This multi-part format makes distributing large business files to or from customers ...

Windows will open RAR files, but to convert files to RAR format, you can make use of WinRAR or these free online tools. We show you how!

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.