Ez most binyelvű lesz.

First of all, we need the Orca MSI Editor, and the iTunes setup package. You can grab it from the Apple site, but the download hadn't started for me, so I recommend the File Hippo site. The latter is light-years ahead of any download repositories.

Then extract the iTunes.msi from the iTunesSetup.exe. It's just a self-extracting ZIP, or something. WinRAR can extract it. I've just pressed Ctrl-PageDown in TotalCommander, and copied the msi to a directory.

Then launch Orca, and open the iTunes.msi.

Find the CustomAction table on the left, then the QuickTimeInstallFailed key on the right.