If you are using an earlier version of Windows you will need a separate utility to open the zip file, like WinZip. If you are using Windows XP, you can simply open the zip file like you would a folder. You will need to unzip the file to get the default.xex file out and put it at a location on your computer.
Save the update as default.zip-it's about 5MB. By downloading this update, you agree to the software license and other related terms set forth in the Xbox Live Terms of Use, located here.