The actress, who played Peggy Mitchell in EastEnders for 15 years, made the revelations in an interview for Piers Morgan's Life Stories.
Speaking of a film premiere that they both attended, she said: "There was this vision, this absolute vision. In the Sixties he was so beautiful. Anyway, in the bar afterwards he came over to me and I said, 'Look, don't waste your time with me, darling. You've got all these lovely ladies after you'.
"And he said, 'Well, when do I ever get to talk to somebody like you?' Well, that did it. That was it. A magic moment. It was great, he was fabulous."
Windsor also admitted that she had a fling with late Bee Gee Maurice Gibb, saying: "I said to him, 'Where would you like to go?'
"And he said, 'Look Bar, let's get it over and done with, let's go to bed'. Because he knew that he wasn't giving it on stage, so we went and had a little moment. It was lovely."
The full interview airs on Piers Morgan's Life Stories tonight at 10.10pm on ITV1.