Replacing Factory sounds on Pa600. How?

[bialk]

page 135 on Reference Guide:

Warning: If you write over an existing Sound, the Sound will be
deleted and replaced by the one you are saving (“overwrite”).
Please save on a storage device any User Sound you don’t want to
lose.
Note: Drum Kits cannot be written over standard Sounds, nor vice
versa.
Note: To save over a Factory Sound location, unckeck the “Factory
Sound Protect” command in the Global > Mode Preferences >
Media page (see page 145).
Warning: When replacing a Factory Sound, please be warned
that all Performance, STSs, Styles and Songs making use of it
will be modified as well. Use this feature with great care!

I have unchecked the "Factory Sound protect", and managed to delete a sound from Factory, but can not write new on his place. I have about 30 mb free PCM memory. What I am wrong?