Based off of your Dxdiag I believe that the issue is your graphics card. It only supports up to Directx 10 and a Directx 11 or higher compatible card is required in order to run the editor.
Here is what we recommend:
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Desktop PC with Windows 7 64-bit or a Mac with Mac OS X 10.9.2 or later
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8 GB RAM
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Quad-core Intel or AMD processor
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DX11 compatible video card
Here is good place to compare and discuss hardware with other UE4 users.
Cheers,
TJ