I knew this was going to come up for me sooner or later. I only barely had enough room on my XBox hard drive to install that stupid 8 GB of Halo 4 data, so instead I inserted a handy 16 gig flash drive and installed to there. The first few times I played Halo 4, I made sure to select that drive. This morning I accidentally selected my XBox drive. It didn't prevent me from doing anything because I was only playing campaign, but after spending an hour-plus doing some legendary, I realized my mistake. So here's what I'm trying to figure out - will this cause me any problems? I know my campaign save data is now on the hard drive and not the flash drive. I don't fully understand though where Halo saves information about my user profile. If I were to beat the entire campaign from this save, would it unlock armor or whatever for my general profile? Maybe I should just copy the game save from my hard drive to my flash drive for simplicity's sake.
Well armor unlocking is based on your online profile, so if you are connected to live when you beat campaign than you should be fine, just like if you recover your gt at a friends house and your online progress is the same back at your house. If you are still afraid of losing any data, there is no harm in moving the files to the flashdrive.
Armour unlocks are saved into the .gpd in your profile itself. You can unlock armours using a save on your HDD, and then do MP/forge on your USB and you will still have your armours.