problem installing itunes

Hi I have previously installed itunes on my windows vista laptop and had no problems. I had to uninstall it recently and I am now trying to download the latest version of itunes on the same laptop but at the end of the installation process a message appears that says "the feature you are trying to use is on a cd-rom or other removable disk that is not available" I click cancel because I don't know what disk it is referring to, and then another message comes up that says "the older version of itunes cannot be removed please contact your technical support group". can anyone help please?