Advanced guestbook 2.2 to 2.3.1 upgrade script

Ok After my last file had some errors I'm hoping this one fixes them. If you are running advanced guestbook 2.2 and wish to update to 2.3.1 simply follow these instructions.
1 - Backup your current files and database.
2 - Download the guestbook from this site.
3 - Upload all the files to your site, overwriting the 2.2 files if you are putting them in the same folder. remember to edit admin/config.inc.php as required.
4 - Download www.carbonize.co.uk/upgrade.zip
5 - Extract the install.php file from the zip and upload it to the same place you uploaded the 2.3.1 files, overwriting the install.php that is already there.
6 - open your web browser and goto the install.php file. eg www.yoursite.com/guestbook/install.php
7 - follow the instructions and let me know.

*BUMP*

I've tried to do this several times but I only get error messages:
Database Error
------------------------------------------------------------------------

MySQL Error : Database Error
Error Number: 1060 Duplicate column name 'thumbnail'

Think I will rewrite the update script from scratch.

I used your script but agin:
MySQL Error : Database Error
Error Number: 1060 Duplicate column name 'thumbnail'

Sorry I should of changed this thread. The new script is at www.carbonize.co.uk/upgrade.zip I will edit my initial post.

*bumped*

*bumped to top*