This was written for the "Defining Moments" 100 word drabble challenge on the Bellatrix Lestrange forum [.net/forum/Bellatrix_Lestrange_The_Dark_Lords_Most_Faithful/56802/] I hope it's good - there isn't a lot you can do in 100 words.
"Slytherin!"
A broad grin broke across Bellatrix Black's face as the ragged hat was lifted from her head and she slid off the stool in the Great Hall, striding towards the Slytherin table and taking a seat.
She'd known it, of course. Yet the word - Slytherin - spoken aloud by the Sorting Hat itself was definite. Confirmation. She had entered Slytherin house, which every member of her family had been in for centuries. It was assuring that she was definitely one of them.
Yet deep down, she knew that from her very birth there had been no going back.