Problems enabling Person Accounts (partially enabled?)

Hi there,

I recently activated Person Accounts on a sandbox.

I am new with PA, but I read that it should create a new Record Type and a new Layout ... after enabled PA it seems didn't create none of them.

When I go to some profile | Object Settings | Account, on "Business Account and Person Account Default Record Types", next to "Person Account Default Record Type" I see "--None--" as the only available option (and before enable PA, the Account object had many Record Types and many Layouts.

How can I explicitly assign a default Record Type for any PA?

Thanks in advance,