I downloaded some repaints from Sim-Outhouse and just made copies of the original planes, changed the names, and dropped 'em in (Like in cfs or cfs2).  But when I went to start up the game all these little messages popped sayin that the .mdl (I think thats what was) files were already in use and it shut down.  So, I tried again and right before it loaded it crashed to the desktop.  It did this several times, even after rebootin', what do I do?

Gettin' rid of the planes didn't work, so I just reinstaled it.  Everything works fine now, and all the planes that I downloaded that worked are still there and all my saved games.