If the installer says a newer version is already installed, you likely have .NET 4.6, 4.7, or 4.8. You don't need to downgrade; newer versions are generally backward compatible.
The .NET Framework is a software development framework from Microsoft that provides a managed runtime environment for apps. Version 4.5.2 was a "highly compatible, in-place update" to versions 4, 4.5, and 4.5.1. net framework 45 2 offline installer for windows 7 top
Because Windows 7 is older, you may need to update your "Root Certificates" if the installer says it can't verify the file's digital signature. If the installer says a newer version is
Why You Still Need the .NET Framework 4.5.2 Offline Installer for Windows 7 you likely have .NET 4.6