UE4 crash when i try to delete an object that is intersecting the terrain

If you run task manager, how much of your ram and cpu are being used while running the editor? It is highly recommend to have a minimum of 8 GB RAM to run the editor, though it can run on lower specs we cannot guarantee it will work or that the experience will be as optimal as if you had 8GB. Can you post your dxdiag here so I can take a look?