There is an important issue which confronts some Drupal users: Whether to make that upgrade from Drupal 5 to Drupal 6 or not? It is not as if Drupal 5 series scores over its elder cousin the Drupal 6.x series. It is a given that Drupal 6 is superior to Drupal 5 taking into view the many enhancements that the Drupal commuity has managed to introduce to the core and contributed modules in Drupal 6. Therefore, it calls for an important decision whether you really want that upgrade from the Drupal 5.x version to the Drupal 6.x version or not.

There might be many contributed modules in version 6 which are perhaps not 100% ready yet and therefore the upgraded version for you would not make any sense. However, since we are now on the verge of seeing Drupal 7 come to light, a switch to version 6 would not be a bad idea considering the fact that it is already in the very advanced state as of now and many fixes and upgrades to its modules are already over as compared to the time when it was newly launched.
Let us now come to the all important upgrade process.

Following step-by-step checklist/instructions would explain the entire upgrade process:

1. Make sure all your modules and themes are available in Drupal 6.x and enjoy active support on the Drupal community.

2. Always backup your original version 5 files and database. This becomes an important savior of an exercise in case you inadvertently botch up at some stage of the installation process.

3. Deactivate all your contributed modules and themes before you initiate the actual upgrade process. These can be upgraded once the actual installation is complete.

4. Disable and uninstall the 'update status' module if you have it before proceeding with your upgrade to Drupal 6.x.

5. Go to Administration >> Site configuration >> Site maintenance. Select the site status as off-line, and save the configuration.

6. Before you begin extracting the Drupal [http://www.ebizontek.com/drupal-services] 6 files and folders to the installation directory make sure you remove all the old Drupal files and folders and start with a fresh installation of Drupal 6.

7. Transfer back the directories: 'Files' and 'Sites' from your backup to the Drupal installation directory.

8. Run update.php by hitting [http://www.abc.com/update.php] (abc being the domain name and path of your Drupal installation)

9. Now download and replace all contributed modules to their latest and compatible Drupal 6.x versions.

10. Now enable the contributed modules by running the update.php file again as described in Step 7.

11. Go to Administration - > Site Configuration -> Site Maintenance and turn your website mode to online and save the settings.

That is it and now you are welcome to the world of Drupal 6