WordPress 2.7 is now the latest version of WordPress and it comes with many new features. Below is the step by step guide line to upgrade your wordpress blog.
[1] Backup your entire blog (Web contents as well as your database).
[2] Rename wp-config-smple.php to wp-config.php and made the required changes in it.
[3] Upload your new worpress files and overwrite existing files.
[4] Now browse http://yourdomain.com/wp-admin/upgrade.php
You are done now.
Note: You can also request us to upgrade your blog on your behalf. Refer this post
Kailash
Thanks for the step by step guideline to upgrade WordPress.