Launching these games freezing the PC so I had to check task manager and my CPU usage boosts to 100 CPU when I launch it.

Fallout 2, Icewind Dale 2, and DIvine Divinity, Arcanum, and Morrowind have this issue.

What confuses me is that I was just recently playing Fallout 2 just fine like a few days ago and only now this problem is a thing.

I tried using the installer I already had for Fallout 2 to do a fresh install and the problem is still here.

Currently downloading a more up to date installer of Fallout 2 from my library to see if this time no problem.

Also how do I make sure this rundll32.exe does not happen again?

That file is just a system file used by applications to run dll files. The problem likely isn't being caused by rundll32 at all. Grabbing the updated installer and reinstalling is a good first step to trying to fix the problem though, so you're on the right track.

I have a ton other GOG games I have installed for years now at the moment and none of them have the issue.

So I don't know why this issue is rather picky and choosy.

Could be introduced by a Windows 10 update. They come fairly frequently and might introduce incompatibilities with GOG games. It wouldn't even mean it's Microsofts fault. It's annoying in any case. Things that work should better stay that way.

I haven't done windows update after some months ago unless its a kind of update that runs in the background.

And I am still on Windows 7 at the moment. Update.

I downloaded the latest installer of Fallout 2 and it works.

So perhaps I have to re download a bunch of installers for games I have.

Glad to hear you got it working.

Worried about some other games like Morrowind though.

Apparently the Morrowind installer I already have is still the same one that I am downloading at the moment.

Just a heads up.... this may be related: https://www.gog.com/forum/general/old_games_not_launching_and_eating_100_of_the_cpu_on_windows_7

I have not testing anything from the post so I can't say it's the same problem.