Assuming that you have an external harddrive formatted to Fat32. Take a pendrive and format it using Xb360. Go to System settings>Storage,etc After its done, plug that pen drive into PC and make a folder named "Content" (without brackets) on it and within that content folder create a folder and name it 0000000000000000 (16 0s). Put the Xexmenu file into that folder i.e. Content/00000000000000/*Put Xexmenu file here*. Now, Plug the pen drive again to your 360, Xexmenu should show up if not then copy the content folder over to your external harddrive. It should appear now!