Do you have Windows Vista or higher and .NET Framework 4.5 or higher? Try reinstalling or repairing your .NET Framework installation.

Have you extracted all the files? Don't start HDT from a zipped folder.

Try reinstalling / updating your graphics card driver

Is there a log entry in the windows event viewer (Windows start menu > control panel > management tool > event viewer > windows log > application)?
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See Problems caused by other programs in combination with HDT