your father might find it a lot easier if you gave him a few introductory lessons and left him to get on with it.
In the past I have worked with a client who got his first computer (Top of the range Sony Vaio)when he was in his late eighties, and it was a bit of an uphill battle for us both.
Has your father any previous computing experience, or is he a complete novice? If he's completely new to computing he'll need some help with concepts to start with, rather than diving straight into Vista. Most elderly people have little idea about computers, and when they first get their hands on one they are completely at sea - they don't understand what the internet is, or what it can do for them. I suggest that before your father tries to do anything you talk to him about what the internet is, and explain the underlying principles of email and web surfing. Then you can talk to him about an operating system, and explain that it is the ocean on which all other software floats. Lots of people have considerable difficulty with this concept, and it's important for your father to understand - you'll do a better job than a book, I think.