If iTunes is still not recognizing the iPad, it is time to try a clean copy of iTunes. To do this, we'll first need to uninstall iTunes from your computer. (Don't worry, uninstalling iTunes won't delete all of the music and apps on your computer.)
You can uninstall iTunes on a Windows-based computer by going to the Start menu and choosing Control Panel. Look for an icon labeled "Programs and Features." Within this menu, simply scroll down until you see iTunes, right click on it with your mouse and choose uninstall.
Once you have removed iTunes from your computer, you should download the latest version at http://www.apple.com/itunes/download/. After you have reinstalled iTunes, you should be able to connect your iPad just fine.