Narrator by Microsoft

Narrator is a light-duty screen reader utility included in Microsoft
Windows 2000 and later. Narrator reads dialog boxes and window controls
in a number of the more basic applications for Windows. While Microsoft
recommends that the visually impaired purchase a full-function screen
reader for general computer use, Narrator is a significant piece of
software because Narrator is included with every copy of Microsoft
Windows, providing a measure of access to Windows without the need to
install additional software as long as the computer in use includes a sound
card and speakers or headphones.
Tech Tip: Narrator can assist a blind person in installing a full-function
screen reader, assisting the user until his/her screen reader of choice is
up and running. Narrator can provide speech when a full-function
screen reader might be unable to do so, such as during the process of
updating hardware drivers.
For more information please visit
http://en.wikipedia.org/wiki/Microsoft_Narrator
Best Regards
Bhavya Shah