beebledeeble Weirdly, that's still .NET 3.5. (CLR stands for common language runtime, which refers to .NET, and 20r3 is a version.) But maybe some other resource isn't interacting with it properly. The first suspect there would be DirectX 9, so please manually reinstall it. You don't need to uninstall; just install over the top and restart your computer. I wrote out how to do it in detail here:
Re: Sims 3 launcher won't open | EA Forums - 8260715
If that doesn't help, please run a repair install of Windows, which will cover a number of bases at once. This isn't a clean install, as in, you won't lose anything; it's just the next best thing in terms of refreshing OS files. Here's how:
https://www.elevenforum.com/t/repair-install-windows-11-with-an-in-place-upgrade.418/
Once you've done that, reinstall .NET 3.5 and DX9 yet again, and then try to play. If that doesn't work, post the new Reliability Monitor error you get when you try (and double-check the time stamp to make sure it's new, not from before the repair install; the time stamps on the graph are a bit weird sometimes).
