How to convert static HTML template to drupal theme
There is no such tool that converts HTML to Drupal theme. But there are services where we can create some kind of Drupal theme with basic regions &amp; templates.

Some modules you can try 


Themer 6.x only
Theme developer
Skinr


Theming Drupal 6 and 7

Modules for theming

A nice screencast for a beginner 
Introduction to Theming Basics for Drupal 7