Why bootcamp update 3.1 wont install?

i have already up and running Bootcamp 3.0 on my macbook pro. I am trying to upgrade my Windows 7 bootcamp drivers from 3.0 to 3.1.

iv been trying to install the BootCamp 3.1 and it keep says ''the bootcamp 3.1 update requires boot camp 3.0 or greater. please install boot camp 3.0 before proceeding with the install of the 3.1 update.'' then i checked bootcamp version and it is 3.0. any idea please...