Where can i go to download Itunes 10.5?

It is because my ipod cant sync to a certain itunes,and it says on the back that i need itunes 10.5 or later,but when i downloaded the latest program,it said "A required Itunes component is not installed. Please repair or Reintstall Itunes." (-45019) Plus it cant even slide to get the wi-fi on. it would be a great relief If you could help me.