http://docs.info.apple.com/article.html?artnum=304424
QuickTime may need to be reinstalled. Follow the steps below to uninstall QuickTime and then download and install QuickTime using the QuickTime standalone Installer.
1. On the Start menu, click Control Panel.
2. Open the Add or Remove Programs control panel and select QuickTime in the list of currently installed programs.
3. Click the Remove button and follow the prompts to remove QuickTime from your computer.
4. Download the QuickTime standalone installer from
http://www.apple.com/quicktime/download/win.html.
Note: There are two options for downloading QuickTime, be sure to select the second option that does not include iTunes.
5.
* If during the download your choose to run the installer, proceed to the next step.
* If you chose to save the download, double click the QuickTimeInstaller file.
6. Follow the on-screen instructions to install QuickTime.
7. Reopen iTunes.
Mac OS X (10.4.8)