iTunes can play or rip music CDs. If you double-click on a song on the CD does it not play successive tracks unless you have it set to shuffle? It will only rip or import the music into iTunes if you tell it to Import CD from the button in the lower right corner of the application. iDVD is not for playback of DVDs, it is for creating playable DVDs using video content created in iMovie. Mac OS X has a dedicated application called DVD Player.app in /Applications for playback of DVDs, and you shouldn't have to manually launch it unless you designated in your system preferences to ignore inserted video DVD discs.