Shoutbox

make sure you have installed all the latest windows updates first.  i think the itunes install needs .net framework (correct me if i'm wrong)

running msi files individually is a BAD idea as it's not a proper install process.

basically just make sure everything else is up to date....then re-download the installer (make sure it actually re-downloads rather than just using the cached one....clear your cache if necessary, or use filehippo.com or something) and then try running it again and tell us what happens