which I am only guessing happened during moving of files from my old Windows XP computer (by a third-party utility).
PC Mover is one of the classic suspects with this.
Let's try the following procedure.
(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):
(2) 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 Bonjour 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?
Thanks for that response, b! You guessed correctly that it was PCMover that I used for the transfer. I've also inspected the transfer report and can confirm that PCMover did transfer Bonjour. However, I cannot tell from the report if PCMover claimed it was OK to transfer or if its compatibility was unknown and I chose to transfer it. If the latter, I would not completely blame PCMover, although it would be nice if it recognized that incompatibility. I probably will not try your procedure until this weekend, but I'll let you know how it goes.
Yeah ... it's a surprisingly powerful utility. (I'm not at all sure how it manages to shoehorn the 32-bit versions into a 64-bit system. Normally, you can't run the 32-bit installers on 64-bit systems.)
The other item to check for in this sort of context (as well as Bonjour and iTunes) is Apple Mobile Device Support. That's 64-bit on 64-bit systems, and plausibly a 32-bit version might have been carried over by a PC Mover migration (if you're unlucky).
Thanks again. Apple Mobile Device Support is another good suggestion. I reported a problem attempting to uninstall that in my other discussion about Safari 5.1.7 that I cited:
The "Uninstall or change a program" Control Panel shows two versions of Apple Mobile Device Support: 22.214.171.124 and 126.96.36.199. I tried to uninstall the older one. The uninstaller started up but quit, reproducibly, in the middle of the process, so that never got uninstalled.
b's knees! That all worked great! Even your step (3) did not contain a typo: the file is really called "Windows Install Clean Up" even though it runs as "Windows Installer Clean Up."
Incidentally, I happened already to have a copy of msicuu2.exe, which I've used once before for a similar situation. In that case, years ago, I used Aloha Bob to transfer files and settings between two Windows XP computers, and it mostly worked well, except that MS Office Pro did not recognize my registration afterward, and I could not reinstall it with the CD(s), so Microsoft tech support told me about Windows Installer Clean Up, which worked and allowed me to reinstall Office.
For my present case, I uninstalled Bonjour (but not Bonjour Print Services) and the older Apple Mobile Device Support not the newer one. I then used only the Safari 5.1.7 installer, and Safari did install properly now, and Windows 7's "Uninstall or change a program" Control Panel shows Bonjour 188.8.131.52 installed. I did not reinstall iTunes, but presumably iTunes can now use Bonjour however it would want to. Thanks for the solution!