For some people, it is incompatible. MapleStory was made for Windows XP, and they haven't updated it to work so well with Windows 7. I have windows 7, and it's okay. There are minor problems; it randomly closes at some points, I don't know any other problems, but if you look them up on google, you'll find out. If you search on basilmarket.com, you'll find other people with the same problem. I don't know WHY you can't run it on your XP. It should be working fine. Try reinstalling it, updating the patch, running it from the website.