I want to change speech into words on a computer – what are the best tools that can allow me to do this?
You can use some online speech to text services: dictation.io, speechpad.pw.
Well, windows 8 has this feature. You can do it using DRAGON NATURALLY SPEAKING software also. I tested dragon and it was working perfectly.
In my opinion, the only realistic option is to go with Dragon Naturally Speaking (or another version of the software). I've not come accross any other package for PCs which is anywhere near usable, and even Dragon is not its faults.
If you have Windows 7 or 8 (and 8.1), you can try the guide here: http://www.howtogeek.com/177539/how-to-get-started-with-speech-recognition-on-windows-7-or-8/. Nuance Dragon NaturallySpeaking is a better alternative, though the cost is around $100USD unless you find a good deal at Newegg or other site that offers deals. Newegg has had recent deals where the cost, after rebate, was below $50USD, and even as low as $2.
As far as any other speech to text software for Windows PC, there really isn't much else worth mentioning. The speech recognition software built into Windows needs patience to work with, but it's free. Dragon NaturallySpeaking works much better, but still needs the training period, and can cost a good bit if you can't find a good deal.
There are quite a few suggestions in a past answer, though it is quite old now it might be of some use to you: //www.makeuseof.com/answers/free-speech-text-software-windows/
Arguably the best of the best is a product called Dragon, from Nuance (http://www.nuance.com), but it's not cheap. They have solutions for Windows, Mac OS X and even mobile devices (you can use an iPhone as a microphone for dictation as an example). You are looking at spending serious money, but some of our staff love it.
Mac coverage, but the same applies to Windows versions: //www.makeuseof.com/tag/control-websites-transcribe-speeches-dragon-dictate-4-0/
A comparison between Apple dictation and Dragon: //www.makeuseof.com/tag/dictate-writing-mac-apples-dictation-dragondictate/
Remember – any software gets better the more you use it, and the more you train it to your voice.