I tried to upgrade iTunes, now it won't install on my computer.

I am having the same exact problem. See my reply to
"Cannot install iTunes 8.2 x64 to my Windows Vista x64 SP" above. This has become a critical issue to me.

"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'

With that one, let's try the following procedure.

First, head into your "Uninstall a program" control panel and uninstall your QuickTime. If it goes, good. If it doesn't, we'll just attend to it when we attend to iTunes.

Next, download and install the Windows Installer CleanUp utility:

Description of the Windows Installer CleanUp Utility

Now launch Windows Installer CleanUp ("Start > All Programs > Windows Install Clean Up"), find any iTunes and/or QuickTime entries in the list of programs in CleanUp, select those entries, and click “remove”.

Next, we'll manually remove any leftover iTunes or QuickTime program files:

(1) Open Local Disk (C:) in Computer or whichever disk programs are installed on.

(2) Open the Program Files folder.

(3) Right-click the iTunes folder and select Delete and choose Yes when asked to confirm the deletion.

(4) Right-click the QuickTime folder and select Delete and choose Yes when asked to confirm the deletion. (Note: This folder may have already been deleted if QuickTime was successfully removed using Add/Remove Programs earlier.)

(5) Delete the QuickTime and QuicktimeVR files located in the C:\Windows\system32\ folder. Click Continue if Windows needs confirmation or permission to continue. (Note: These files may have already been deleted if QuickTime was successfully removed using Add/Remove Programs earlier.)

(6) Right-click on the Recycle Bin and on the shortcut menu, click Empty Recycle Bin.

(7) Restart your computer.

Now try another iTunes install. Does it go through properly now?

Outstanding! That did it for me but I will offer the following

On my Vista Business system even though I run as adminstrator and should have had the ability to delete the folders and sub-folders, I could not. To solve the problem I went to "program files" properties and changed the ownership from SYSTEM to Adminstrator and then had to re-boot. After that there was no problem in doing the delete. It was also interesting that I could re-name the iTunes folder but not the Quicktime folder, this prior to the change in ownership. I suspect that now I should change the ownership back to SYSTEM unless you know of a reason why I should not.

Thanks again!