Wiibrew strongly recommends that you do not update your Wii through Nintendo.
Version 4.0 of the System Menu was released on March 25th, 2009. It was announced in Satoru Iwata’s GDC keynote.
The announcement lists these changes:
* The Wii console can now use SDHC (SD High Capacity) Cards with a maximum of 32GB of storage.
* The SD Card Menu, which allows you to launch titles directly from an SD or SDHC Card, is added to the Wii menu.
* The Wii Shop Channel will now allow you to download titles directly to an SD or SDHC Card.
* The Wii console’s Data Management menu has been enhanced to make it easier to copy and move stored items on an SD Card or the Wii console’s system memory.
* There are other behind-the-scenes enhancements to the Wii console system menu included with Wii Menu 4.0
The update includes a batch of IOS updates issued a few hours before the System Menu update.