For some reason, If you don't own a Motorola droid or a Google nexus one you can't use the speech to text functionality on android devices.
If your device doesn't have support for Speech to Text feature, you will have to install it manually.
The problem is that this feature doesn't exist for some reason on the Android Market, so we will do it in the tricky way
What is an APK file?
An apk file is “android package file” with the extension ‘.apk’ use to install any application on Google Android powered mobile phone. So in case you need to install any application on your android phone you need to have file with .apk format.
Installing any application on Google android is pretty easy but installing non market apps on android phone is little tricky one. Well don’t worry, here we go.
1. Download Google Speech to Text apk file from here: 4shared.com - online file sharing and storage - download VoiceSearch.apk
2. Copy the file to your SD card, and push the card to your mobile device
3. Install and open the Apps Installer application from the Android Market (This opens a view showing *.apk application names in the sd card root directory)
4. Select VoiceSearch.apk file you just downloaded
5. Restart your mobile.
Enjoy, and don't talk too much to your phone