why doesn't my computer or iTunes show my phone

hi. I have followed every recomendation by apple: restarted phone, checked usb cables, downloaded newest version of itunes, tried trouble shootong through msconfig, still my HP computer with 32 bit vista 2007 or Itunes wont even recognize my phone. cant sinc, cant download jpgs or pics. very frustrating and time consuming. any one kow how to fix this?