I have my MediaSmart 3.0 update and 2gig ram upgrade ordered, looking forward to updating my EX475 soon.
Terry Walsh of We Got Served has a overview of the process:
You may order you update for $25 +shipping from HP:
2. support and drivers
3. step 1 – select download drivers
4. step 2 – select product, ex475 in my case
5. select operating system of your pc that you will use to do the upgrade
6. Continue with your order