I am using os visa home premium , which has only service pack 2, on it, i downloaded the latest itunes program. It said that you need service pack 3, which itunes can i use.

The Service Pack 3 requirement only applies to Windows XP. The current version of iTunes is stated to be compatible with any edition of Vista (though many users have reported an issue with spurious errors generated when closing iTunes). See turingtest2's user tip on Troubleshooting issues with iTunes for Windows updates for advice on the steps that may be necessary to achieve a successful installation of iTunes. Apple's support page on How to restart the Apple Mobile Device Service (AMDS) on Windows - Apple Support may also be relevant.

Note also that Microsoft will cease all support for Windows Vista in less than 2 years' time, so you may also want to look at options to upgrade to Windows 8.1 or (from July 29) Windows 10.