Diffraction from the crystal structure of diamond anvils, which are used to hold the sample and apply pressure, affects the output data and causes problems in their interpretation. The XTurn 1.00 program simulates X-ray diffraction of diamond and was designed to help the experimenter to optimise diamond cell orientation in order to reduce the number or even completely remove diamond diffraction spikes in high pressure dispersive EXAFS data. The diffraction obviously depends on the cut of the anvil face and the energy range of the X-rays. Careful choice of these two parameters can significantly increase the quality of the EXAFS data. The program allows the user to set vertical and horizontal angles gradually for any X-ray energy range and follow the changes in the resulting diffraction due to the diamond. It is assumed that the anvil face crystal plane indices ,are "known and the incident beam is 'white' over the given energy range. We assume also that planes with reciprocal indices greater than 9 do not contribute greatly to the scattering due to the large distances between atoms. The XTurn 1.00 program runs under Windows95/98/NT and has a very simple user interface and Help support. The code was written in Borland C++Builder.