Knowledgebase
How to migrate from Joomla 1.5 to Joomla 1.7
Since the upgrade from 1.5 to 1.7 involves greater changes and is more complicated than, let's say, from 1.6 to 1.7, it's rather called a migration. This migration can be achieved with the help of a plugin called jUpgrade which will perform all the actions needed for the completion of the migration process.
Before you start anything, make a backup of the Joomla files on your account and of the database used by the Joomla installation.
First, if your Joomla 1.5.x is not the latest version (the last one is 1.5.23), upgrade it. You can find different upgrade patches from the download section of the official Joomla site. Download the one you need (e.g. 1.5.20 to 1.5.23) to your local computer, unzip the archive and upload the unzipped files and folders with an FTP client to the root Joomla folder on your account.
Keep also in mind that during the migration process to 1.7 any changes to core Joomla files will be lost.
Before you begin the migration itself you need to download jUpgrade and install it as an extension from the backend's Extension Manager.
You also need to go to the Plugin Manager and enable the plugin named System-Mootools Upgrade.
After that go to the Components menu and select jUpgrade. You'll see a big Start Upgrade button in the middle of the screen. Before you click on it however, you can click on the Parameters button in the upper right corner. A window will open with different options that you can configure.
You can change the version to which you want to migrate (1.6 or 1.7), you can change the table prefixes for the database of the old site (that's in case it's different than the default jos_) and also the database prefix for the new site. If you leave all the Skips options to the default No, jUpgrade will perform all the actions described there. If you set some to Yes, you'll have to do those manually.
If you make any changes click on the Save button in the upper right corner of the window. Then just click on Start Upgrade.
Once the migration is complete, if you haven't changed the default folder from the Parameters window, you can find the new site in the jupgrade folder inside your Joomla root directory (e.g. public_html/joomla/jupgrade). At this point you can back it up just in case.
If you want your new site to be accessible at the usual URL address (the one for the old site) and you still want to keep the old site, first copy all the files and folders from the root Joomla directory, except for the folder with the new site, in a newly-created folder (e.g. old). Then delete the files and folders from the root directory, except for the folders with the old and the new site, and copy the files and folders from the folder with the new site (e.g. jupgrade) to the root Joomla directory. You can do those things from the Files section of the Pixie control panel. When you want to remove the old site just delete the subfolder containing it and then you can also delete the database tables for the old site through phpMyAdmin.
For some more details check out the tutorial on migrating Joomla from 1.5 to 1.7.