Simple harmonic motion energy conservation problem

[al_famky]

Homework Statement

A mass m hanging on a spring oscillates vertically. If the equilibrium point of the oscillation is a distance d below the relaxed length of the spring and if the amplitude of the oscillation is A, what is the maximum kinetic energy of the oscillation?2. Homework Equations

The Attempt at a Solution

I did this:
mg=kd \rightarrow k=\frac{mg}{d}
\DeltaE=\frac{1}{2}k(A+d)^{2}-\frac{1}{2}kd^{2}=\frac{1}{2}\frac{mg}{d}(A^{2}+2Ad)
which wasn't the answer, but i don't know where i went wrong.
if anyone could point out the problem, i'd really appreciate your help

 

[TSny]

There's another form of potential energy that needs to be taken into account.

 

[al_famky]

There's another form of potential energy that needs to be taken into account.

which is?

 

[TSny]

Note that the mass is moving vertically. Think about all of the forces acting on the mass.

 

[al_famky]

Thank you very much, TSny, for your help, I get it now.
and this question wasn't supposed to have been posted here, sorry for the mix up.