When I load my SD card, the one that came with the 3DS, into my computer it says that I have to format the disk but it will erase everything that is already on there like my saved data from SSFIV and the Mii files as well. Am I screwed? I made sure the SD card wasn't locked. It's working find in my 3DS but just not in my PC.
Well maybe your computer doesn't support things like that. I tried to put music from my computer into the SD that came with the 3DS but when i put it in the 3DS it didn't show any of the music. Maybe they just don't support eachother
This is hard.
But first, SSFIV data goes on the game-chip itself. It does not get saved on the SD card.
Try it! Remove your SD card and you will see that you still have your data.
As for the Mii's, well I guess its gonna take some minutes to make them again.
SSFIV and the Mii Maker Only store "Extra Data" on the SD card. Your Mii Data is stored in system memory. Your SSFIV data is stored on the SSFIV game cartridge.
I believe that the "Extra Data" is used for StreetPass and SpotPass, so your 3DS can receive SpotPass or StreetPass data without the SSFIV or other SpotPass/StreetPass capable application being installed or running.
By default, any photos you take with your 3DS will also be stored on the SD card, but you have the option of storing photos in system memory.
As for the PC asking to Format your SD card, this should not be required. Have you had problems with other SD cards in your PC's SD card reader?