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I solved the problem (stuck ancient UE4PrereqSetup_x64.msi package that wouldn’t uninstall without the original .msi, which i didn’t have anymore) using a tool from Microsoft - Fix problems that block programs from being installed or removed .
This finally managed to uninstall the ancient package and thus let me install the new .exe version of it.
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Sorry to necro this thread, but i can’t fix the problem without using the “-SkipBuildPatchPrereq” option.
This solution does work but you can’t use it from the Epic Launcher.
I am stuck with the installation of the prerequisites, they are looking for a Dreadnought game that i apparently had years ago. It’s now stuck and the old version can’t be uninstalled, the new one can’t install over it either.
Anyone know what to do?