Somehow a 4GB SD card with D40 images on it got mixed up with the fresh ones. I put it into my D7000 and it said "this card contains no images". Fortunately, I did not format the card or make any photos. Later, my daughter needed a small card for her D40 and I gave her that one. She put it into her D40 and then informed me that there were a bunch of images on it. I think the D7000 firmware should have told me there were D40 images on the card instead of lying to me. So now I know I'll have to check cards in the computer because the cameras will lie.
Set up the camera to your preferences and save the settings to the SD card. I keep a tiny SD card (32MB) for just that purpose in my kit bag. I also store my custom picture controls and the most recent firmware on the card so I always have it with me. Also transfer the settings to your computer for safe keeping.
In fact I never format my SD cards. I don't believe that it solves more problems than it creates. I just have the files erased after they are copied to my PC. The things that you can do to corrupt a memory card are not mitigated by periodic formatting and I prefer to have my settings saved on my larger memory cards as well to return them back to my default shooting settings.
I consider the settings file I keep on the SD card my "U3" settings. Ido use the U1 & U2 positions but just as I can flip to U1 or U2 and have the camera in a known state, I can also load the settings file and I am in my third default known state.