So...

I have Vista Ultimate RTM installed on both my home and work laptops and decided that I want to install iTunes. iTunes has been my media player of choice for some time now.

I remembered trying to install it on RC1 and RC2 and it failing to install Quicktime.A check on the Apple forums found some similar issues. When downloading iTunes to my RC1 machine, there was a link to a survey on the download page where they asked you about your experiences with installing iTunes and QT on Vista.

I had exactly the same problem on RTM. Talking to other people, those who upgraded XP to Vista have iTunes working OK. The problem seems to be with the install of QuickTime (possibly something to do with its interaction with User Account Control). On a hunch, I went to www.oldversions.com and downloaded iTunes 4.2 (the latest is 7.0.2) which installed (and worked) perfectly although it wouldnt let me sign in or access the UK iTunes Music Store (iTMS).

As soon as I opened iTunes 4.2, it alerted me to the fact that a newer version was available.

I then reinstalled the newer version on top of 4.2. This time I had a different issue. When I had my issue installing iTunes on RC1 of Vista, I found an article by Dan Warne on how to install iTunes on RC1. It was no help to me that time but on this occasion I had the exact same error. There are a few minor UI differences but Dan's solution worked and i'm now on the latest version of iTunes and can even purchase from iTMS.