Not good, unless your friend is working with channeling, has the proper protection, and invited this specific dude to come in and take over.
If he didn't ask this spirit to come in, that is bad news indeed. My advice in that case would be to bring in someone who can move that spirit along to where it needs to go. 45 minutes is a very long time for a spirit to be in possession of one's body, and that in itself says to me that this is a potentially problematic situation.
This is a thread from awhile back, when I was no longer a subscriber, but now I am one again (thanks to a lovely person here on A.T.) and I am reading this and wondering and hoping your friend hasn't had anymore issues with this.
I'm with Apollonia and BrightEye too that this is a potentially dangerous situation that your friend needs to find some help with.
I know a person who had something similar happen to him. He remembers being woke up while he was sleeping by a spirit who tried to to take over his body. He was terrified by this and luckily for him, he called out for his guides help--but he tells me the story of a mighty fight to get this spirit to leave.
This person is a psychic - medium, but now refuses to embrace his abilities and use them for fear of this happening to him again, even though he did the right thing calling on his guides to help him. Luckily this man I know, knew what to do immediately and it helped him.
The problems with this is that if a spirit takes over your body, you may not be able to shake it out and be in a sort of limbo state, I imagine. I'm not 100% sure, but it does bring up some thoughts of that old movie, "Exorcism".
I do hope your friend was successful in getting help with this and not having anymore issues with this troubled spirit.