Q: I want to uninstall iTunes 8 and use iTunes 7. will my back up disks form iTunes 8 work? Thank you.
A: Whether or not you will be able to do this depends largely on the type of backup you have made from iTunes. iTunes 8 made some significant changes to the iTunes database structure, making the new database format completely incompatible with iTunes 7. This means that if your backup was simply an archival of the iTunes folder to a CD/DVD or to an external hard drive, you will not be able to open this in iTunes 7.
Note that iTunes would also have made a backup of your previous iTunes library database, which is stored in a folder named Previous iTunes Library. This database, however would only be up to date as of the date you updated to iTunes 8, so it may not be particularly useful for downgrading unless you have update. very recently.
The good news, however, is that backups of your iTunes library using iTunes’ own “Back up to Disc” feature can be read by iTunes 7.6 or later and used to restore your iTunes library from these backup CD or DVD discs. If your iTunes 8 library is still intact, you can make a backup using this method prior to downgrading to iTunes 7. Once you’ve downgraded to iTunes 7, simply insert the first backup CD or DVD into your computer and iTunes will automatically offer to restore the backup set for you.