XCD's were big back in the day before DVD burners were around, when people wanted better video quality without having to burn two or three CD's for one movie. What XCD did was strip out all the error correction on a file, allowing you to fit 800mb on a 700mb disc. They were pretty cool until they got scratched, which was true of most CD's. One of the tricks to making them was that you had to use a video format with error correction. AVI has no error correction, but .ogm and .mkv both do, and so those were the major formats that people used for XCD's. Once a file was encoded onto an XCD, it changed format slightly, which is why all mode 2 files have the .dat extension. A (small) filter was needed to play these files. You can find one here. Or, if you aren't reading this from the past, you can use Dat2FileGUI to turn the .dat back into a regular file. To make an XCD, you can use Mode 2 CD Maker GUI. There's a great picture below of my MAIN MAN #1 NIGGA whose name I'm totally forgetting making an XCD of hellraiser. The big file, an .mkv, is bolded after he used Set/Unset Form2. You only want to use that for one file, the one with the movie. Leave everything else at regular size. All of these programs work in windows and if you use linux you're totally out of luck lol.