Despite reports suggesting his wife Debbie's willingness to move back to the London area was the reason for the transfer, he says: "It had nothing to do with where Debbie wanted to live; she was quite settled and never had a problem with the north east.
"She had moved to Sheffield and Merseyside before that, and we were OK in Sunderland, but I think the offer Sunderland had was too good for them to turn down, so there was no question on that score.
"I think the fans were different class up there but it's great to be playing for the West Ham fans again - they will see a better player than last time."
By his own admission, his first stint at Upton Park was not a great success, and he admits: "I was only a kid, a bit immature - and I've grown up a lot over the years.
"I needed the kick up the backside when I went to Sheffield; we were bottom of the first division.
"I will never forget what Howard Kendall did for me - he resurrected my career and then took me to Everton as well.
"I have followed West Ham from a distance since I left and a lot of my mates are West Ham fans.
"I hope we can win something this year and give the fans something to shout about.
"Hopefully the next few years will be the best of my career."
Don, who has signed a four-year deal, adds: "I must thank Craig Brown for letting me go to the hospital for my medical - he was very helpful."
And he dismisses talk that West Ham are in for a tough season, adding: "I wouldn't have come if I thought it was going to be a relegation battle.
"Glenn likes to play football like all West Ham managers have done, and I hope we can turn that into winning football as well.
"And I'm looking forward to seeing John Moncur again - he is a great lad and a great player!"