Modeled and rendered in Blender.
However, I think Miku-Chan looks too happy. And I'm going to quote Yu-Gi-Oh BBT Abridged here when saying my first reaction.
"I'm going to tear the happy right out of your soul."
Lolz. I love that line.
I cannot say about the modeling because I did it in different sessions, but took awhile.
My computer is around average too. It certainly isn't a beast.
Characters are quite a different beast than designing parts. They come with their own set of challenges, such as likeness, hair, flowy clothing, etc.
But the knowledge/experience you gained from modeling parts (by "parts" I'm guessing you mean engineering components?) should definitely help in modeling characters.
Miku is cute ♥
Same body really.