What about available settings of user' s assistant function in Windows Vista?

Please refer to the following contents
 
The settings of user’s assistant function can be performed in Ease of Access Center.
Ease of Access Center can be displayed in the Control Panel.
The following are the primary settings.
•Magnifier
For users who are visually impaired or who are editing a picture want to magnify the screen, they can use the magnifier tool which can creates a separate window that displays a magnified portion of the screen.

•Please refer to the following relative solution.
 
[Windows Vista] How to set Magnifier

•Narrator
•Narrator is a text-to-speech utility program in the Windows Vista for users who are blind or have impaired vision. Narrator can read most of the text displayed on the screen.
Please refer to the following relative solution.

[Windows Vista]How yo use narrator

•On-Screen Keyboard
•On-Screen Keyboard is a tool that displays a virtual keyboard on the screen that allows users to type data using a pointing device or joystick.
•For detailed contents, please refer to the following relative solution.

 
[Windows Vista] About On-Screen Keyboard

•Sticky Key
•This option sets Sticky Keys to run when you log on to Windows. Instead of having to press three keys at once
(such as when you must press the CTRL+ALT+DEL keys together to log on to Windows) you can use one key at a time by turning on Sticky Keys and adjusting the settings.
Detailed settings can be carried out by Make the Keyboard easier to use of Ease of Access Center.   
•High Contrast
Set the match color of High contrast.
High Contrast heightens the color contrast of some text and images on the computer screen, making those items more distinct and easier to identify.
Detailed settings can be carried out by Make your Computer easier to use of Ease of Access Center.
•Filter
This option sets Filter Keys to run when you log on to Windows. You can set Windows to ignore keystrokes that occur in rapid succession, or keystrokes that are held down for several seconds unintentionally.
Detailed settings can be carried out by Make the keyboard easier to use of Ease of Access Center.