Getting Rid of Non-Tris and Non-Quads
Since convertxsi.exe cannot recognize meshes that have polygons with more than 4 sides, all polygons in your model have to be either triangles or quads.
1) Press Space Bar to go into Object Selection mode and click on the model. The wireframe of the model should turn white.
2) Go Select > Select n-sided polygons > Five Sides or more.
3) If the wireframe stays white, then you are still in Object Selection Mode and your mesh does not have any polygons that have more than 4 sides; proceed to Section B “Creating the UV Map”
4) If on the other hand the model’s wireframe turns yellow, then you are now in Polygon Selection Mode and all the polygons that have more than 4 sides have now been selected for you.
5) While in Polygon Selection mode, hover the mouse pointer over the model, and then Alt+RMB-click. A context menu should pop-up.
6) Click on “Hide Unselected (Ctrl + Shift +H)”. Now the only polygons showing are the non-tris and non-quads.