In the movie Star Trek: First Contact, the crew of the Enterprise travel back in time and witness the Borg working to prevent Zefram Cochrane's first warp flight. They then decide to directly intervene with events to allow history to take the course they learned about in school, where Zefram Cochrane's warp flight is a success and the Vulcans initiate first contact with the humans.
My question is whether these events (the Borg attack on Bozeman Montana and the Enterprise crew's efforts to "restore" history) were always a part of history, or if the actual facts of history were changed by the actions taken by the Borg and the Enterprise crew, even if the outcome was the same.
Quite possibly relevant: in the ENT episode "Regeneration," which features the Borg as the featured enemy of the episode, Captain Archer recalls a story that Zefram Cochrane once told of people from the future coming to help him out (an obvious reference to the events of Star Trek: First Contact), but that Cochrane later retracted these statements.