If you mean online: the website that hosts them are known to be a bit on and off. That is something I am looking into correcting in the future (setting up my own server for people to play on), but for now it is all there is.
You mean in the quest program on windows? You install quest, download a .quest file and open the .quest file. The quest580 file is only the program used to play the games that come in .quest form.