Can I upgrade previously purchased music to iTunes Plus?
Yes. Any available upgrades will be shown on the Upgrade My Library page (Music received for free is not eligible for upgrade.). You can upgrade all music at once by using the Buy button. This replaces all music you've bought previously on iTunes with available iTunes Plus versions of the same music. You cannot choose which songs, music videos or albums to upgrade individually. Song upgrades are available for $0.30, video upgrades for $0.60, and albums for 30% of the album price. iTunes Plus music will continually be added to iTunes, so check back often to find new music available for upgrading.