Try using different resolutions on the computer monitor to see if that changes the placement of the stimuli to the desired position.

Once you find the screen resolution that you want, it is advisable to set the screen size in the Options part of your styles.drt file to the same setting as the screen resolution of the monitor. You can find information about how to set the screen size here in the DirectRT manual:

http://www.empirisoft.com/directrt/h...creen_size.htm