Change home computer for Ipod touch

My son has Ip an ipod touch, (purchased last year xmas 2009) think its the 3rd gen. When he got it we had a different computer which he initially logged as his home computer. This has since broke and we brought him a new laptop for xmas. I have authorised this laptop but I am unable to access the apps properly through Itunes. I want to be able to manage them, delete etc but I am unable. Can anybody advise how I can change the home computer to the new laptop so as I can properly manage the apps on the ipod??? Thanks