This build comes as a bunch of files (originally it was in a .exe), it contains a update and a SP1.cab.
It doesn't update the build number itself but rather adds the Multimedia Update
behind the RTM build.
It updates several components included in Windows such as Media Player to version 5 which is now called Windows Media Player
Internet Explorer and Outlook Express are updated to Service Pack 2.
There are more images available in the gallery.