If they are not my skyboxes then they are rubbish, that's a well know and respected scientifically proven fact known by most boffins and general smarty pants.
I don't think the evil ones will help you, so the saviour of FPSC the good shepherd that I is will help a lost sheep.
Off the top of my head, (funny how one can do something, but has to sop and remember when one isn't looking at it) Go to file then build game, it will open a box. its the second option down, click on that, then scroll down and find skybox, click on it and change it to another .x file that is found in your skybox files.
