There is no boot disk available.
When they say boot disk. They are talking about the the CDRW or DVRW that they have created with all the files you need to have on a xbox. For example you have boxplorer evox x, xcommander,xbmp,xbmc,avalaunch,etc... on the cd so they derived with the conclusion of ccalling it a boot disk because what it does it that it boot when you have in the xbox. Well i hope some did understand it now.