I upgraded from windows 7 32-bit version to 64-bit ("custom install" - tried using LapLink's "Windows & Upgrade Assistant". Big mistake, but that's another story.) Afterwards, I downloaded 64-bit version of iTunes, and have had many, many problems getting it to install and run. Following instructions and advice on both Apple support and MS forums, and elsewhere, I have unistalled, reinstalled, repaired, uninstalled, deleted files/folders, used MS Windows Install Cleanup Utility, reinstalled, etc., etc. with varying degrees of partial success. Today, I was finally able to successfully launch QuickTime (installed by itself), but now, when I run the iTunes installer, it stops suddenly and I get the following error message: "Could Not Open Key: Unknown\Components\DA42BC89BF...(32 digit address)\Another HUGE address name Verify sufficient access..." I have Admin rights, so I don't know why the installer can't access this key (registry key?).