Sound like the old bait and switch routine. What you need to do is do a virus scan then log off when you restart you should do a file search for anything with the ending '.exe' and write them all down. This may take a few minutes because there will be thousands. Then call microsoft and ask to talk to Ron Mexico, that's my cousin, and email him the list. He will be able to intertwine the all of the halo 1, 2, and 3 maps into your computor so than all you need is a cell phone and your chance to flex skills on ampex. Are you with me? good.
Then go into your kitchen and get all the tin foil you can get your hands on and in the room that your computor is in cover all the walls in tinfoil. This is imperitive. If you skip this step you risk total meltdown level five. Then sign up for on bungie again and it should work.
Best wishes.