After watching the TV airing of CoS tonight, I had some questions and went back to the book for answers - I never like to base posts on the movies as they can change things around too much.
So, in both the movie and the book, when
Harry enters Tom Riddle's memories in the diary, he follows him to Dippet's (Hogwarts Headmaster) office where Dippet tells Tom that under the current circumstances, they cannot allow him to stay at Hogwarts over the holidays and that he would be safer at the Muggle orphanage.
Tom says, "Sir - if the person was caught - if it all stopped . . . "
It seems his only motivation for not letting the basilisk out anymore was so that he wouldn't have to go back to the orphanage.
He is obviously embarrassed about his heritage by his reddened face when Dippet asks about his parents and he has to say he has a Muggle father. This leads me to believe that at this point, he was somewhat normal. He simply didn't want to have to go back to the orphanage, so he stopped letting the basilisk out in the hopes that he would be allowed to stay at Hogwarts.
So, he wasn't completely bad to start off. JKR has already told us that he has never loved anyone, so we know he wasn't
completely normal, but he seems to have normal teenage concerns (fitting in, etc.).
Do you guys think his motivation for framing Hagrid was to stop the worry over the basilisk to stay on at Hogwarts and just be normal or do you think it was to stay on at Hogwarts and further explore the Chamber/work on his hostile world takeover . . .

?
If it was to just be normal, was this a critical point for Tom Riddle? Would he have turned out differently if they had let him stay at Hogwarts that summer? Or was he just the ruthless killer from the start?