Problems installing iTunes 10.2.1 -installation source is not available

Question

I've tried to download the upgrade to 10.2.1 a number of times with no success. I keep getting the error message:
Windows Installer
The feature you are trying to use is on a network resource that is unavailable.
Click OK to try again, or enter an alternate path to a folder containing the installation package "iTunes.msi" in the box below.
But when I search for the installation package I can't find it on my computer anywhere.
I've tried uninstalling iTunes but it won't let me do that for the same reason. It says: The installation source for this product is not available. Verify that the source exists and that you can access it.
Can anyone help me please?

Answer 1

The feature you are trying to use is on a network resource that is unavailable.
Click OK to try again, or enter an alternate path to a folder containing the installation package "iTunes.msi" in the box below.
Unfortunately, this sort of trouble has gotten more complicated to deal with ever since Microsoft pulled the Windows Installer CleanUp utility from their Download Center on June 25. First we have to find a copy of the utility.
Let's try Googling. (Best not to use Bing, I think.) Look for a working download site for at least version 3.0 of the Windows Installer CleanUp utility. After downloading the utility installer file (msicuu2.exe), scan the file for malware, just in case. (I use the free version of Malwarebytes AntiMalware to do single-file scans for that.)
If the file is clean, to install the utility, doubleclick the msicuu2.exe file you've downloaded.
Now run the utility ("Start > All Programs > Windows Install Clean Up"). In the list of programs that appears in CleanUp, select any iTunes entries and click "Remove".
Quit out of CleanUp, restart the PC and try installing iTunes again. Does the install go through properly now?
(If you do find a clean download site for the correct version of CleanUp, please don't tell me where it is. Without wishing to sound paranoid (although I grant it does sound paranoid), there is a non-zero chance that posting links to download locations for the utility here at Discussions leads to that download location being shut down.)