I letterbombed my wii using a 16 gb SD card and now I want to install Priiloader on my Wii. However, when I insert my SD card into my computer, my computer can't read the card. It says that I have to reformat the card. Should this be happening?

No, it shouldn't; what is the message exactly? My SD card is detected as problematic by Windows, but I can say no to it scanning (and possibly formatting) it.