Hi:
NVDA stands for Nonvisual Desktop Access, and is a completely free open source screen reader for Windows. In my humble opinion, it is by far the best screen reader available. I'm sure others will disagree though; preference of screen readers tends to be as inflamitory a topic as Vi verses Emacs. Anyway, if you want to download a copy of NVDA to test out yourself, you can find the project website at:
http://www.nvda-project.org/