Search for sys files:

When I open the Zip-file I only see an empty folder. Where is the sys file?

You need to be able to view hidden files. Follow the instructions: Open Windows Explorer (not IE) - usually it is c:\windows\explorer.exe. Choose "Folder Options" Choose "View" Choose "Show all files" in "Hidden files".

I'm unable to open the Zip-files, since they are asking for a password to unzip the file.
Our files are not password protected. You probably just need to upgrade your current unzip software to the latest version.