Without the Multi-Targeting Pack, Visual Studio will either refuse to load the project or will silently "retarget" it to a newer version (e.g., 4.8), potentially introducing breaking changes in serialization or cryptography.
Are you trying to for an older project, or are you looking to set up a legacy development environment? Multi-Targeting Pack for the Microsoft .NET Framework 4.0.3 microsoft .net framework 4 multi targeting pack
: If you are working on a modern system (e.g., Windows 11) but need to build an app for an older environment that only has .NET Framework 4.0, this pack allows you to do so. SDK Components : These packs are often installed automatically alongside Visual Studio or as part of a Windows SDK Build Servers Without the Multi-Targeting Pack, Visual Studio will either