Not sure what all of that business in the reply above about running TomTom Home was about. Unless the firmware on your unit happens to be "old", the tweak that makes the ASR happen is of the manual do-it-yourself variety.
First, I don't know whether all 720's were originally delivered with the core of the speech recognition included or not. Mine certainly was. However, in the US, none of them were "activated".
In order to activate yours, you will want to connect your 720 to your computer, and respond "Yes" to your 720 when asked if you want a computer connection.
As for TomTom Home, if it comes up, you can just shut it down. It plays no part at all in this process.
You will find that your 720 is recognized as though it were some kind of external USB hard drive (like a "thumb drive", if you know what those are), or as many digital cameras are today (except the devil Sony, going its own way as always).
So you can click on "My Computer", and behold, you'll see your 720 there looking like a hard drive that can be opened.
Click on it. One of the folders you see should be called "ASR" (Auto Speech Recognition). Click on that. It should have a fair number of files in it that start with "acmod3200". If so, you're good to go. If not, you should first assure that the *current* level of software is loaded on your 720. Docking it and letting TomTom Home do its magic will take care of that. I don't know how far before firmware version 7.221 the folks at TT may have incorporated the ASR pieces.
Assuming you are up to date on your firmware, you just need to add one tiny file that contains JUST the number "1" to cause all of that software to work. The file you need is called "support_asr.dat". Once that file is placed in the "ASR" folder, you're done.
The way most people have created this file is to open Notepad, hit the "1" key exactly once (don't even hit "Enter") and save that file to the filename mentioned above. If the name gets a little munged (get's a .txt stuck on the end) by Notepad, just rename it to the name shown.
This system won't allow *.dat files to be attached, but I'm going to attach mine here as a *.doc file (it will have to be renamed from "support_asr.doc" to "support_asr.dat" after it is downloaded). Click on it, save it to your hard drive, rename it, and slide it over into that "ASR" folder, and have fun!
The ASR software handles some basic information for providing destinations, etc., and can be used for speaking town names, street names, and street numbers. I've even told it "NO" in English when it asks if I want to reroute based upon traffic conditions. The instructions should have been in your manual, since the 720/920 seem to share a lot of the same manual information.