If you have a newer installation of Office, there may be some "built-in" speech recognition capabilities that could be useful. It appears to be available for any Windows operating system (Win98SE and on) but does require OfficeXP or later. The stuff provided is intended for dictating into Office programs, and additional software/hardware would be needed for full control of your machine, but it might be worth looking at what's already there.

I haven't gone very far with this, but you could start with:

WD2002: Speech Recognition Frequently Asked Questions

The above article cites:

For additional information, click the article numbers below to view the articles in the Microsoft Knowledge Base:
     278927 WD2002: General Information on the Installation and Configuration of Speech and Handwriting Recognition
     283160 WD2002: Handwriting Recognition Frequently Asked Questions
     295947 HOW TO: Troubleshoot Speech Recognition Problems in Word 2002

For the most up-to-date information about speech recognition developments at Microsoft, please browse to the following Microsoft Web site:

http://www.microsoft.com/speech/

John