If you must use a legacy tool found online, never run it on a machine connected to your main network. Use a "Sandbox" or a Virtual Machine (VM) with no internet access to test the file first. How to Find It Safely
Check reputable communities like PLCTalk or Control.com . Often, veteran engineers have archived versions of these tools and can provide them via private, trusted channels.
A company moves their operations to a new PC and needs to re-authenticate their legacy design software.
The manufacturer has discontinued the product, leaving users to turn to third-party archives.