With the release of the new WordPress 2.5, there are a lot of new WordPress users however there are a big base of people who would like to use the capabilities and the new features of WordPress 2.5 however they are unable to because they fear breaking something however an upgrade can be done seamlessly without involving any risk at all, in case anything goes wrong, it can be fixed in a couple of minutes and everything would be back to normal on the old version. There are two methods of upgrading depending on the type of web host you have.

VEXXHOST WordPress hosting
All of our web hosting plans come with Fantastico which enables you to install/upgrade/uninstall over 52 scripts, instead of going through this document and following the instructions, Fantastico will simply tell you that you need to upgrade your script, all you need is to click on upgrade and Fantastico will backup your old version, upgrade your WordPress install and upgrade your account.

Other web hosting platforms

• Download the new version of WordPress from http://wordpress.org/download/.
• Backup your database, you should do this, most of the time people are lazy and do not do this however considering this is a major upgrade, it’s a big risk to take, I would strongly recommend backing up your database, that can be done by logging into your web hosting control panel and using a utility such as phpMyAdmin to take a dump of the MySQL database so that you can restore it incase anything goes wrong.
• Backup your files, now this will be important so just in case everything goes wrong, we’ll put back the old set of files and the old database so everything will be back just like the way it was on the first place and so that you can get the least downtime possible. This cannot be skipped else you’re taking a very big risk and the work it takes to back it up will be a lot less than having to eventually re-install everything from scratch. I suggest downloading it to a directory on your computer
• Update all your plug-ins and de-activate all of them so that you can make sure that when upgrading, the plug-in will not cause any unexpected problems by new modifications to the code rendering your website unusable, your best option would be to deactivate them so that you will face less problems when performing the upgrade on your WordPress blog, this is very key step when upgrading as it might just break your new install.
• You should go into the directory where you have extracted the new WordPress 2.5 install and go to your directory where you have your old backup, copy over the contents inside wp-content/themes however not including the “default”, copy over wp-content/uploads and the wp-content/plugins directory however make sure you do not copy the “akismet” or “hello.php” files from the old installation as these have been updated and are now obsolete.
• Once you’re done with that, upload everything back and over-write everything as you should have a backup of your old website if you properly followed the steps as there is no risk over-writing.
• Run the upgrade script by going to your site, it is located in the wp-admin/upgrade.php so you would have to go http://yoursite.com/wp-admin/upgrade.php depending on your website, follow the instructions that have been given to you by the script to upgrade your WordPress installation
• Reactive the plugins by logging into the control panel and your WordPress upgrade should be complete by now, make a new backup of the new database just in case!