I also have this issue and b noir's question identify's part of the problem in finding a solution. The error message I receive does not identify the file or feature. I have tried to uninstall iTunes through Control Panel, but that also results in a similar error message.
I also cannot manually move songs from my iTunes to my iPod. The files do appear in my iPod libraries, but they are greyed out and will not play. This may be related to my installation problem, but I won't know until I solve that issue.
The error message I receive does not identify the file or feature. I have tried to uninstall iTunes through Control Panel, but that also results in a similar error message.
If you're getting sschap's message when uninstalling iTunes, that usually narrows things down to trouble with the iTunes.msi.
(1) Download the Windows Installer CleanUp utility installer file (msicuu2.exe) from the following Major Geeks page (use one of the links under the "DOWNLOAD LOCATIONS" thingy on the Major Geeks page).
Here's a screenshot showing the particular links on the page that you should be clicking:
After clicking one of the circled links, you should be taken to another page, and after a few seconds you should see a download dialog appear for the msicuu2.exe file. Here's a screenshot of what it looks like for me in Firefox:
Choose to Save the file. If the dialog box does not appear for you, click the link on the page that says "CLICK HERE IF IT DOES NOT". Here's a screenshot of the page with the relevant link circled:
When the dialog appears, choose to save the file.
(2) Go to the Downloads area for your Web browser. Doubleclick the msicuu2.exe file and follow the prompts to install the Windows Installer CleanUp utility. (If you're on a Windows Vista or Windows 7 system and you get a Code 800A0046 error message when doubleclicking the msicuu2.exe file, try instead right-clicking on the msicuu2.exe file and selecting "Run as administrator".)
(3) In your Start menu click All Programs and then click Windows Install Clean Up. The Windows Installer CleanUp utility window appears, listing software that is currently installed on your computer.
(4) In the list of programs that appears in CleanUp, select any iTunes entries and click "Remove", as per the following screenshot:
(5) Quit out of CleanUp, restart the PC and try another iTunes install. Does it go through properly this time?