Unable to open Itunes / Quicktime.

"C:\Program Files (x86)\Common Files\Apple\Apple Application Support\zlib1.dll is either not designed to run on Windows or it contains an error. Try installing the program again using the original installation media or contact your system administrator or the software vendor for support."

Okay ... you've got a damaged Apple Application Support dll there. That's what is causing the iTunes and the QuickTime launch errors. For a bit more information on the relationship between iTunes, QuickTime and Apple Application Support, see the second part of this user tip (The "The relationship between iTunes and Apple Application Support" bit):

http://discussions.apple.com/thread.jspa?threadID=2355263&tstart=0

Doublechecking something before proceeding ... do you currently have a copy of Safari for Windows version 4.0.5 installed on the PC? (That makes a bit of a difference as to how we proceed, because that will determine what version of Apple Application Support we will need to have installed on the PC.)

No safari, but I can get it if that is required.

No no, you're fine without it in place! We're going through a phase where the Apple Application Support version required by the latest Safari for Windows version (4.0.5) is higher than the one in the most recent iTunes and QuickTime installers. So I just have to be careful at the moment (when swapping out people's Apple Application Support) that I don't stuff up people's Safari in the course of trying to fix their iTunes and QuickTime ...

Okay. So what we're going to try this time around is uninstalling both your iTunes and Apple Application Support. Then we'll reinstall iTunes, which should also reinstall your Apple Application Support. We'll take a few other explicit precautions too, just in case.

For the appropriate 64-bit instructions for your setup, see the technique I recommend to fizzylove in the following thread:

http://discussions.apple.com/message.jspa?messageID=10918603#10918603

More problems, apparently I'm completely missing AppleApplicationSupport.msi and I can't uninstall Apple Application Support.

Quite possibly with that one your AppleApplicationSupport.msi is fine ... unfortunately, the AAS versions 1.0.1 and 1.1.0 didn't cope particularly well with uninstalls and repair installs if AAS *program files* were missing. (I could replicate that one at will on my XP Pro SP3 box by dragging files out of the AAS program files folder onto the desktop and then trying to do a repair install.)

But no matter ... whatever the particular cause of the missing AppleApplicationSupport.msi error message, the treatment is the same.

I'm assuming here you were already able to succesfully uninstall iTunes.

Download and install the Windows Installer CleanUp utility from Microsoft:

http://support.microsoft.com/kb/290301

Now run the utility ("Start > All programs > Windows Install Clean Up"). In the list of programs that appears in CleanUp, select any *Apple Application Support* entries and click "Remove".

Quit out of CleanUp, and restart the PC. Now start again with the fizzylove instructions at the "removing leftover program files and folders" stage.

Do things proceed okay from then on out?

🙂 Excellent news. Glad things are sorted for you.