JKR's Theme SPOILERS

[LadyMyneh]

No: HPFGUIDX 62791

Harry's Parselmouth abilities were given to him by Voldemort, but 
that's not what the Sorting Hat was considering when it suggested 
putting him in Slytherin- the Sorting Hat instead focused on Harry's 
ambition and desire to prove himself- and I don't think they came 
from anywhere by Harry's heart.

As for Neville, I do think he has a great deal of innate magical 
talent, and it is most likely that he's been suffering from a block 
most of his life- every year when he visits his parents, he sees 
first hand what horrible things magic can do, and it scares him that 
he has this power too. He's let fear rule him for most of his life, 
but now that he's letting his bravery shine through, he's overcoming 
his block.