Clients Old WP Version 2.3.1 – Best Way To Update

A new client of mine has finally accepted that he needs to update WP and has given me the task of updating his older version. It was only when I got into his admin and to my sheer horror, saw he was running V2.3.1. from 2007!

The problem is that this version doesn’t allow for auto-updates so I’m wondering if it’s even possible to update is or should I just bite the bullet and start with a fresh install? If it were not for the fact he’s got over 300 posts, I’d certainly just go for the latter but if there is a relatively painless way to update this old version, I’d be delighted to hear it.

Thanks in anticipation.