- last post: 01.01.0001 12:00 AM PDT
Try reinstalling - the registry file may have been corrupted. If that is the case, then you'll probably want to remove all the spyware from your computer. If reinstalling won't help, you may want to do a complete uninstall and then install Halo once more (This is not the same as reinstalling) - I'm not sure which option fixes corrupted registry files.
The worst case scenario is that somebody jacked your cd-key and is using it. They may have done this using a keygen. It's highly unlikely, however...
Try that and let us know if it works.