Uh.... how do I put this gently... There is NO simple way to upgrade Joomla 1.0 to Joomla 1.5. To go from 1.0 to 1.5 is a migration, not an upgrade. That is because 1.5 is a complete rewrite of the entire system with a completely different core. You have to do a sanity check first before even attempting to migrate. First, does your site use a LOT of third-party extensions? Do you have a large member base? If not, then things are easier. However, if you answered yes, things aren't so straightforward. In either case, you first of course need to the following: 1) Back up your site! That is ALWAYS a first step. 2) Create a "test server" and copy our current Joomla 1.0 site to it. You will work off of THIS copy. If your site currently has members, etc., and works fine, it makes no sense to risk it needlessly. 3) On that same test server, create a separate Joomla 1.5 installation. You should create a new directory if you will just for Joomla 1.5. Unzip the Joomla 1.5 to that directory so it's ready for installation. For me, that means using WAMP on my local PC, but you get the general idea. Full migration instructions are provided here: http://www.siteground.com/tutorials/joomla15/joomla_upgrade.htm (Note: This site will also refer to to the official Joomla documentation as well). NOTE: The migration only handles CONTENT. If you have a lot of third-party components, things get a LOT more complicated. The Joomla migrator only saves content, NOT extensions. The smart thing in that case is for you to make sure you do Step 1 that I listed above CAREFULLY. The most important thing to save is your DATA TABLES!!!! (Sorry, I don't usually yell, but I cannot emphasize enough how important this step is). Once you've successfully migrated your Joomla 1.0 database (assuming you're using the migration script instructions provided via the link I posted above), you can then install Joomla 1.5 on your test server, and during the install you will load the migration data (which is really an SQL file export of your Joomla 1.0 that should be 1.5-ready). Then, lastly, you need to get 1.5-native versions of your existing extensions. Fortunately, the "major players" pretty much all have these available. Just be forewarned that some extensions that were free for J!1.0 are now commercial. And this is pretty much the gist of how to go about migrating. Of course, take your time, as the actual steps will take more than just a few minutes. A complex site can take several days (if not longer) to migrate properly.