Tired to delete spam comments in your drupal site? Why don't you install CAPTCHA module  for your site. It will help you prevent from spambots.

What is CAPTCHA

A CAPTCHA is a challenge-response test most often placed within web forms to determine whether the user is human. The purpose of CAPTCHA is to block form submissions from spambots – automated scripts that harvest email address from publicly available web forms. The CAPTCHA module provides this feature to virtually any user facing web form on a Drupal site.

Installation

1. Download CAPTCHA module (for Drupal 5 and Drupal 6)

2. Upload CAPTCHA module to your web hosting : /public_html/modules/

3. Enable CAPTCHA module : admin/build/modules , you will see in spam control section: CAPTCHA, Image CAPTCHA and Text CAPTCHA (just enable CAPTCHA and Image CAPTCHA) and Save

4. Use this page to configure CAPTCHA module : admin/user/captcha

5. Configure CAPTCHA and Image CAPTCHA Tab, enable "Add CAPTCHA administration links to forms". Choose which form_id you would like to put CAPTCHA, for example comment_form and contact_mail_page.

6. Configure Image CAPTCHA. By default you will see just one font type, you can add True Type font if you don't like the default one. Download True Type fonts from this site and upload to your web hosting : /public_html/modules/captcha/image_captcha/fonts/

And now you can see image CAPTCHA in your comment and contact page. :)