I need help with simulation by ModelSim

Dear Dave

--- Quote Start ---

The simulator does not know what you want for the initial value for Q. Supply an initial value for the signal, eg.,

    -- Difining signal(s)
    signal Q    :    std_logic_vector(25 downto 0) := (others => '0');

and it will work fine.

An alternative method is to add a reset input and then add reset logic to the counter process.

Cheers,

Dave

--- Quote End ---

I did the way you told me and it worked fine!!

Thank you very much and I'm soooo happy now because this had been bothering me like 12 hours...