On gpcinema you can only play xvid or divx (to my knowlege). Both are .avi but with different codecs. You can easily convert basically any video using virtualdub. The only ones you might have a problem with are wmv and quicktime files. You can change quicktime files through the quicktime player into a format you can convert but the wmvs will be harder (go here for a guide how to do so). You can get a guide to converting to gpcinema here. Or if you want to convert from a dvd then go here.