Is there a way to force this to install and is that a good idea ?
Whoa! Let's
not go rolling back a couple of Windows Installer versions at present ...
Apologies for the delay ... I've just been doing some experimentation on my XP SP3 system.
I determined my Windows Installer was at version 3.1 v2 ("Start > Run", type
msiexec and hit enter). So I downloaded and installed the Windows 4.5 redistributable for XP, installed that, confirmed (by msiexec again) that I had the 4.5 version of Windows Installer in place, and then uninstalled my iTunes 9.0.3.15. After that, I ran ASU and it detected the iTunes + QuickTime 9.0.3 update for me.
... So we're not just looking at a "4.5 bad, 3.1v2 good" thing here. Something pretty subtle must be afoot if there's a Windows Installer 4.5 issue on your PC (the fact that you're able to uninstall and reinstall things without issue speaks to that).
One more experiment for the day. (I'm a bit overloaded with other ongoing troubleshoots at the moment, and I owe a bunch of people replies ...)
If it's a really subtle issue with Windows Installer underlying the ASU issue, maybe we can get some joy if we employ the equivalent of a gentle tap with a small rubber hammer: Let's try
reregistering the Windows Installer Service as per *Method 1* from the following document:
[How to resolve Common "Windows Installer" Problems|http://support.microsoft.com/kb/555175]
... any better luck with getting ASU to display available updates after that?