Just what are the Borg?
I don�t think they�re a race. I think she�s it. I think when she says I am the Borg, she is the Borg. Everything that she assimilates simply becomes an extension of her. Her minions, her tools.
I came to the conclusion that she�s always been there. Rather as energy cannot be created or destroyed, I just think the Borg queen has always been there and in First Contact she chose to manifest.
She was just pure energy, like a force of nature and has always been here. We encountered her for the first time in Star Trek: First Contact, but that was just because she chose to assume a material form. So I know they�ve killed her off twice, but don�t believe it. She may not ever come back, but she�s still there. She�s not to be disposed of.