7-Zip not working from the DOS prompt or command line?

You'll need to add the binary to your machine's PATH

See more here: http://www.7-zip.org/faq.html

You can either copy 7-Zip to a well-known path like these:

C:\Windows\system32
C:\Windows
C:\Windows\System32\Wbem

or you call 7-Zip with the full path:

C:\Program Files\7-Zip\7z.exe

Or you do the thing Screenack said ;)

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