What OS are you using on your PC? Windows? English? Did you allow explorer to view hidden files?
Run Chkdsk on the drive and allow it to fix error automatically
If that doesn't help, backup your drive (useful data only), delete all partitions and re-create a Primary, Active partition then format it to Fat32, 32K cluster. Use Easeus Partition Master which is easier than Windows' standard utilities.
Copy the data (only those you really need) back to the drive and try it on your Wii again.
If that still fails, may be your drive requires more power than the Wii can supply or it is dying
btw, what drive are you using and how old is it?