Is it legal for someone to give you a computer & then after many months demand it back?

I have a "friend" that I used to do some work for. I would run an aspect of a business for him & care for his dementia & terminaly ill wife 24 hours of the day. He gave me a computer back in May as a friendly gesture and because I was working for him for free. In july I moved in for 2 months to help him out more. He knew this was temporary. Then I moved out a few weeks ago. Now he wants his computer back and claims he never gave it to me. Even after he told a bunch of people that he did in fact give it to me. Is this legal?