I am not a relationship expert, but let him know that you will only be friends. No need of justifications and don't get manipulated. If you don't feel right about it, it's your life and stay away from getting involved as you may regret later.
You may not appreciate the advices given to you in the comments, but they are well meant because people care. Now it is up to you to follow them or not. Good luck.
RE: XP no longer supported.
You are right Z, it would be your best move.