no printer shown on I pad, I phone 4s or I Pad

I have a new printer HP Officejet6600, all set up fine just cant print from my Iphone 4s Ipad or Ipod, It says it is compatable for air print, my other HP printer didn't work either but the Epsom one did, could it be the operating system on my computer (vista) thats stopping it.

It is so frustrating as I am a cub leader and need to print often.

Thank you