For the most part, the zip file functionality built into Windows XP and Vista is adequate for nearly all your zip file needs. However, inevitably you are going to come across an invalid or corrupt zip file which Windows cannot open. When this happens, try opening the same archive using 7-Zip.

I ran into this situation twice last week. One of my users could not open a zip file, but when I tried the same file using 7-Zip, it worked without a problem. As it turns out the zip archive had an extra ‘layer’ inside of it which Windows could not read. Once the user downloaded 7-Zip, they could access the files with no problem.

Now, 7-Zip is not a miracle worker. If the zip file truly is corrupt, there isn’t much you can do about it. 7-Zip offers a “Test Archive” functionality which helps you identify corrupt files, but if the test passes you should be able to open the archive.