There are at least four reasons why you might see the message This installation package could not be opened when trying to install WinZip.
If this message displays when you attempt to install using the general evaluation version EXE file (such as winzipxxx.exe), it may be due to increasingly restrictive security settings or antivirus application settings. This file is a self-extracting Zip file which extracts an MSI file (winzipxxx.msi) and possibly other optional offers to the user's Temp folder; running the install from there. In some cases, simply downloading and using the MSI file to install corrects the issue.
Please try the following:
If you browse to a shared network folder and double click on an MSI file there, you may see the error message described. In this case, you should copy the MSI file to a local drive and then double click it in that location.
This error message can also display if you did download a WinZip MSI file (winzipxxx.msi) as described above. This would mean that the MSI file did not download completely, which resulted in an invalid file. When downloading, you should choose to Save the WinZip MSI file. Then, when the file has completely downloaded, you will need to locate it in a folder window and click on it to display its saved size.
If your internet browser does not display the size of files being downloaded, checking the saved size will not be be a guaranteed method for determining if your download was a success. You can at least make certain that the MSI file is not extremely small (it should be in megabytes, not kilobytes).
A third possibility is that you have registry settings that do not allow for long filenames during an MSI file install. To check this:
After closing the Registry Editor, please try installing WinZip again.
If you have any questions, please email Technical Support.