Question about Window's Installer?

I am trying update my itunes to 10.2.1, so I wont loose all my data on my new iphone. I have a 2008 HP Pavillion dv6000. However, midway through installing the update to itunes, my computer crashes. The problem is in my window's installer. The update crashes midway through installing. I have McAfee total protection on my computer, and does that have any effect? My window's operating system is window's vista.