Need help updating iTunes

<p>I got a new iPod touch but can't use it because I have iTunes 10.3.1 (I am bad about updating things). I need at least 10.5. I go through the whole process updating to the new version from the iTunes website. It says installation complete but iTunes has not changed when i re-open it. Anyone know what I am doing wrong? Could not find much info online so thought I would ask here. I am running Mac OS X 10.5.8 if that matters.</p>