Hey Alucard123 -
I know I am repeating my answer here to antoinepavia but it will help me get this issue down to the exact problem:
Let us start from the beginning and work through your problem.
First Uninstall and delete all your engine files. You should not have to remove any project files.
Next got to Epic Games/Unreal Engine’s Release page on Git Hub, here
Download the 4.2.1 Release files: Source Code.zip, Required 1of2.zip and Required 2of2.zip. If you need to compile in VS2012 OR have projects that rely on dependencies in VS2012 then you will also need to download the Optional.zip. (This will take a while.)
Next unzip the files in the following order into the directory of your choice. (For me I use D:\GitHub\Unreal Engine.): Source Code, Required 1of2, Required 2of2, and [Optional if needed]. Merge Folders as you unzip (They will all have files that go into the Engine sub-directory, for instance.)
Once fully unzipped, Double Click on Generate Project Files.bat and wait for the file to run.
Once completed you should now see two solution files, double-click (open) the VS2013 solution file.
In VS2013, Build UE4. (This will take a while.)
Once the Build is complete, you should now have the UnrealEditor.exe in your Engine/Binaries/Win64 subdirectory.
Ok, So make sure you follow these steps and let me know step by step where how each step is working.
Thank You for your patience,