click it and in the roll down menu click preferences ( at the bottom )
on that sub menu pop up you will see a tab at the top marked Viewports,
click that,
now near the bottom right is another tab called choose driver,
click that,
You now have three options, l think the default is Heidi, you need to select either Direct3D or OpenGL, l use OpenGL as that has the fastest and smoothest rendering but your graphics card may prefer Direct3D, select the one you want,
click ok,
reboot Gmax and it should be ok,
if not, select one of the others, one of these will suit your system.