What is a good training program for a skinny 45 yr old man?

Just be grateful you aren't battling the "battle of the bulge" like most of the people in the Western countries. Even Governor Arnie was a scrawny kid when he was younger, but determination will get you more muscle on your thin frame. Join a gym that has a good trainer (not someone who may be there one minute and not the next.) If you can afford it get your own personal teacher to train you in weights. Just don't do the steroids!