Verify if the files can be unzipped successfully from 7Zip archive
You can use 7zip to do this. Either right click and select Test Archive from the 7-Zip context menu or you can use the command line
7z t somearchive.7z
7z t somearchive.zip
etc
You get output like this from the command line
"c:\program files\7-zip\7z" t somefile.7z
7-Zip [64] 9.20 Copyright (c) 1999-2010 Igor Pavlov 2010-11-18
Processing archive: douglas.cx.txt.7z
Testing somefile.txt
Everything is Ok
Size: 761
Compressed: 492