when the download completes, and I go to install it. I get a message saying this: This installation package could not be opened. Contact the application vendor to verify that this is a valid Windows Installer package.' What do I do?

Where did you download this? I am on a Windows 7 machine and downloaded the 64-bit version of 2.9.2. It installed ok for me. Can you do a screenshot of the error you are receiving.