How to merge/combine files with extensions .001, .002, .003.. etc? [duplicate]

The files have likely been split by a compression program. 7-Zip should handle them fine. They could also have been split with hjsplit or a similar tool, but 7-zip should handle the files.

"A lot of the other answers assume that the files are parts of a RAR (or similar) archive. If, on the other hand, they are simply split files and you want to recombine them, there is a simple way:

On Unix systems, just use cat - it's what it was made for - concatenate. Just cat foo.001 foo.002 ... > foo.combined and you're done.

On Windows, the simple, unassuming command line copy command can in fact also do this, but you must remember the /B switch."