I've read that the microphone quality & placement is very important too.

Quite a few people with repetitive strain injuries use speech recognition software. That's how I learned about it.
I got Via Voice back in 1999, but haven't had to use it for quite awhile.

There are some free ones that you can try out also.

http://www.e-speaking.com/

some of these are trials and some are free,
http://download.cnet.com/windows/voi...torsRating+asc
{you can sort by clicking on the left side of their webpage}

Built in on Vista - I didn't know that.

Accessibility in Windows Vista
[Windows Speech Recognition
Windows Speech Recognition in Windows Vista empowers users to interact with their computers by voice. It was designed for people who want to significantly limit their use of the mouse and keyboard while maintaining or increasing their overall productivity. You can dictate documents and emails in mainstream applications, use voice commands to start and switch between applications, control the operating system, and even fill out forms on the Web.]
http://www.microsoft.com/enable/prod...ta/speech.aspx