Why would you tell him to change USB loader GX to Gecko OS, that has nothing do with his problem ><
What exactly is your problem now anyway? You want to format it back so that your computer will recognize it but it doesn't work? That's weird, I know for a fact I formated my flash drive from wbfs back to normal.
Anywho for the wii to regonize it, it needs to be in wbfs format so unless you want to use it for something else there's little point in formating it back. If you just want to get isos on there you'll need this program
http://wbfsmanager.codeplex.com/