"If you redo college again, what would you major in?"
I already explained this a little in another question about restarting your career. You can use the same answer here if you want, but I will give one more example of not changing your major in the long answer section.
Short Answers
"I didn't realize I was so interested in computers until I graduated college. So if I could select a different major, I would major in Computer Science."
"I liked the fact I completed my degree in English. But if I could redo college again, I would like to double major in English and Business."
"I would liked to have majored in Engineering. I have a strong interest in hardware so I believe Engineering would have helped."
"I would choose to major in Marketing in the Business School. I really enjoy this type of work and having more background would have helped me to excel more."
Long Answer
"If I were to redo college again, I don't think I would change my major. I liked the fact that I majored in Business and I believe it will help me with my career. I'm pretty good with the computer, but I would like to have taken more computer classes. Because technology is growing so quickly, I think I would have benefited from having a deeper understanding in computers."
This answer demonstrates a good choice in the beginning. I included the portion about computers because they want to see something you would have done differently. And making the comment about computers shows the interviewer your understanding about technology to some degree. But don't say this answer without first stating that you are pretty good with the computer.