I don't have an xbox, but it might be the same sort of method as transfereing files to a mp3 player...Give it a go anyway...
Connect your xbox to the comp (I'm assuming this is done with a USB cable)
Go to you shared folder outside of limewire (to find this folder click on one of you files in the limewire library and hit explore, your shared folder will then appear...you can close down LW now if you want)
Right click on one of your files
Select send to
Select the drive your xbox is plugged into (mine would be E Drive)
That should be it (I hope
)