Shell - 2013-12-14

Have you already deleted the original files? If so, it is bad - you have no possibility but to brute-force the password. I think it is a good idea to test an archive straight after its creation. You can do one more thing though - create another big archive with a known password and test whether 7-Zip can open it. If it cannot - there is an error in 7-Zip 9.20 itself.

I cannot help you further, except for a brute-force code (it will NOT work if there are spaces in the password):
for /f %a in (passwords.txt) do (
7za l -p%a Q_Drive_17-09-2013_20-28-24.7z
if not errorlevel 2 echo Found a password: %a