sync mail clients between windows xp and osx

I am attempting to help my grandfather in his decision to buy a new computer. He has been very impressed with my mbp and is very interested in a mac pro. He is a programmer who writes programs for midi players and uses yamaha synthesizers extensively. He needs to be able to acces files from both xp and osx, he also needs to be able to read and write emails using microsoft office in both osx and xp. So is their a way for him to have both copies of microsoft office synced with one email account?

Is dual booting a viable option for him or should he just stay on a pc?