Yup, under the advanced tab in Itunes, there is a options tab, then there is an option to change the type of file to convert too. Look for Aiff and mark that, then when u select the song u want, click on advanced and then convert selection to aiff.
ok. go to itunes, preferences, click on the advanced tab. Then click on the importing tab. If u look below, there is a tab that says Import Using: "insert coding here". Yours is set on AAC. You can change it to AIFF here.