What do you mean hidden? what's the filename? Updated where?

I have just downloaded the 5.01.01 upgrade zip.

In the documentation folder this is what the Readme.txt file says:

Application Upgrades

- make sure you always backup your files/database before upgrading to a new version
- BACKUP your web.config file in the root of your site
- unzip the code over top of your existing application ( using the Overwrite and Use Folder Names options )
- rename release.config -> web.config
- merge any localized settings from your old web.config to the new web.config. These typically include:
  - connection strings ( SiteSqlServer )
  - machine keys ( validationKey and decryptionKey )
  - objectQualifier
- browse to localhost/DotNetNuke in your web browser
- the application will automatically execute the necessary database scripts and provide feedback in the browser

Having done an upgrade before I know this is out of date (the automatic XML merge thing described elsewhere in this thread does the trick).