Now when I start up Call of Duty 4, it loads up to the screen, asking if you want to play Multiplayer or Singleplayer. I chose Singleplayer, the page went away and an error popped up saying the "Call of Duty 4: Modern Warfare couldn't write a file. The hard drive is probably full." But I don't think the hard drive is a problem because I have 94 GBs left. Is there a fix for it?