HyperLens
Hyperlens works basically like if you had an adjustable magnifying glass in your hand. Really helpfull for low visions. Many configuration possibilities (especially Autorun options, convenient for people who have difficulty with computer). Simple to install (no need to reboot). But it's just free for 30 days, then 50$ for one computer. HyperLens can be really helpfull for visually impaired people. For "Zoom text" users, Hyperlens has a full screen mode too. Hyperlens is not really free, but it isn't too expensive for a single user.
