That's the reason it got the error. -looks at confused faces- Let me try to put it in another way..... When you have RMXP, or RMVX open and editing your games (or just starting them) do you any other programs running, like Windows Media Plater, Itunes, Virus Scanner (any scanner), Internet, or any other program running other then RPG Maker? My brother had a few of his games have that error, and he had a few programs running while working, and like Polraudio said in the quote, the TeamViewer was running and we got the error messege as well. But I never had an "Unexpected File Format" happen to me to any of my games (unless if you count the one I'm working on with Polraudio) since I only have XP or VX running and nothing else. (I use my Ipod to listen to music while working :P). But I'm not officially sure on this theory of mine, there is proof that it has happened, but did everyone have another program running when they had XP or VX open?
(Wow, that's a lot.)