Here is a quick guide on what you need to develop modules for Drupal, with useful links to get you started.

First, you need to know what is Drupal is, and what it can do.

You then need to learn PHP, if you do not know it already.

After which you have to setup a development environment. You need a computer of course. If you are using Windows on a PC, you need to download and install XAMPP from ApacheFriends.org. Of course, if you do not use Windows, and have Linux or Mac OS/X, then you need Apache, MySQL and PHP on it.

You then need to read Drupal's Contributors' Guide, which has sections on coding standards, API description, and a specific section on how to write Drupal modules.

With a little practice, you can become a Drupal developer. 

If you want some more reading and resources, please visit the Drupal Windows specific pages.