Today I'm going to introduce you all to a new method TAMIL writer which you need not want to memorise the keys for letters and such other horrible things.
This is an easier one , because you jujst want to pronounce your word in english and type the appropriate letters for that so it'll change those letters into words .

click here for download and click here for user guide about how to install.
But in my opinion just install and change the language from the language bar OR press Alt+left Shift to change the language in your computer.
just try this . i"ll hope that u'll enjoy this to type in tamil....
Thank You.