If you are looking for free/no cost then NVDA is one way to go http://www.nvaccess.org/
Depending on level of vision left JAWS, Zoomtext, Magic, and ~~Windows Eyes~~ are all options but they cost money. Like a lot of money. There are circumstances that local Division of Blind Services would help pay for these things so having your dad connect his client with the local Division of Blind Services office would be beneficial.
They also can help with a lot of other resources and training.
Edit: If you have Microsoft Office you can get Windows Eyes for free at
$1