The elusive negative zero on the HP 30b

[FabioBrasil]

This has nothing to do with settings, I believe.

But it probably is because you are treating it like classic RPN and doing this:

a) 55555 [+/-] [Input] [shift] [Y^X] => 0.00

While for Entry RPN (used on the 30B) you must do this:

b) 55555 [+/-] [Input] 55555 [+/-] [shift] [Y^X] => -0.00

I also think it has nothing to do with it. Perhaps that ² (from SW 4 5 2010 ²) explains something.
I did it both ways a) and b) and the result was 0,00