Richard, I have been using window-eyes demos, with GWMicro's permission. 
System access needs an internet connection but works very well.  Thunder is 
free, but will only work on XP machines or later, the same is true for 
system access.  It does demand text only settings for e-mail and it's own 
text only web browzer.  NVDA works well, but I find it's interface is 
difficult for people who are new to computing.  JFW will only let it's demos 
work for a pre-determined time.  Therefore you'd have to install new screen 
readers ever four months or so.  Not what I want to try to do.  I also 
install talking typer, math flash, word web, talking calculator, and make 
wordpad the default program for both text and .doc files.