This has been a big headache for me for ages - Text I enter within iTunes, especially the comments field for MP3 files, is often missing in the Windows folder where my iTunes music is stored. It also often vanishes completely or appears as garbled code (just a series of numbers and letters, each 8 digits long) when the file is backed up. This is strange because I've bought an extra program that easily backs up my iTunes library - and it always reproduces all the metadata...