Dunne said: "It was difficult. Obviously I made my home there, but they made it quite clear that they didn't want me there any more.
"So for me to have the opportunity then to come to Aston Villa was brilliant. I could have maybe sat there at City and played in the reserves for the next three years, but for the manager here to show the faith that he has done and put a bid in was pretty pleasing."
Dunne added: "I'm not hurt to leave City, I'm just hurt the way in which it was dealt with. It wasn't the best way they went about things, but that's a different story.
"For me, I'm just pleased to be here at Villa and looking forward to many years playing at a club that's stable. I'm looking forward to the future."
Dunne is relieved to have completed his move after the Premier League asked for more time to survey the paperwork after the transfer window closed.
He said: "It was a long day and the transfer window is frantic. I think that's the same case for everyone. It always makes people nervous so just to get through at the last moment was quite a relief.
"It's brilliant to be here. I was at Man City for nine years and it was probably time to go our separate ways.
"I just feel now for me it's a fresh start and hopefully I can bring here all the experiences I had at Man City and the things I learnt to benefit Villa."