My formated HD(with games) doesn't work on my wii, but works on my friend's wii.
Not actually that it doesn't work but like some games get errors (Mad world puts into black screen when I press new game, Tales of symphonia: DotND hangs as soon as I fight the 1st blue monster on the game's first dungeon).
black screen = missing ios's
Your friend probably ahs some updated ios's that you are missing. Thats why you have problems with some games.
You should also check to make sure you have latest versions of other things like the USB loader, cIOS38 rev14, etc etc