SetCurrentDir( "Storagecard/Media/Others/" )
OpenToWrite ( 1, "Storagecard/Media/Others/myfile.txt", 0 )
is redundant since the path has already been set, try
SetCurrentDir( "Storagecard/Media/Others/" )
OpenToWrite ( 1, "myfile.txt", 0 )
or simply
OpenToWrite ( 1, "Storagecard/Media/Others/myfile.txt", 0 )