R00

R00 file is part of multi-volume RAR files.

Some RAR files can be parts of multi-volume sequences. When a huge archive is splited to a few smaller files. They may have extensions .rar (the first volume), .r00, .r01, ..., or .part1.rar (the first volume), .part2.rar, ..., etc.

To unpack those volumes, place all them to the same folder and start extraction from the first volume. WinRAR or 7-Zip can do the job perfectly.