Hit the Start Menu, type cmd.exe and Right Click then choose Run as Administrator.
So, before I ran iTunesSetup again, I needed to "lie" to the installed by making a directory link to where QuickTime actually got installed. Since both apps are 32-bit apps running on 64-bit Vista, they are each installed to "c:\program files (x86)." Apparently iTunes has hardcoded "c:\program files" so iTunesSetup goes looking for QuickTime in "c:\program files\quicktime" rather that where it really ended up. However, I hadn't put iTunes on my new Vista 64-bit system, and I was shocked to see the iTunes installer fail to install saying "cannot find Quicktime." A little file system sniffing solved the problem.
We're going on a trip tomorrow so I needed to get my iPod setup quickly and sync'ed beforehand.