When trying to install or uninstall a piece of software, an error message appears "An Installation Support File Could Not Be Installed."

According to the InstallShield Support site: "This error occurs if the InstallShield engine files aren't installed and registered properly. "

Our first suggestion is to take the effected computer into a repair shop. Since InstallShield is relatively standard on all copies of Windows, seeing this error code could mean that there are larger issues that need to be resolved, which would be best handled by a Windows technician.

If you would like to try troubleshooting the issue first, we suggest the following page from the InstallShield support web site:
https://consumerdocs.installshield.com/selfservice/viewContent.do?externalId=Q108497&sliceId=1
The site can also be reached by going to the following web address:
https://tinyurl.com/7v7zvu4

Following the Install link on Step 1 of that page will have you first remove the current copy of InstallShield, then download and install a fresh copy.
If that doesn't work, Step 2 the site will also give an option to manually register a file that can sometimes effectively become unlisted in Windows.

Once those steps are complete, you should be able to install or un-install the software as usual