iTunes cannot run because it detects an issue with QuickTime

Symptoms:

You may see an error message when attempting to open iTunes 7.7 or later stating that "iTunes cannot run because it detects a problem with QuickTime."

If this issue occurs with iTunes 7.0.2 - 7.6, customers may instead see this error message:

"iTunes cannot run because it has detected a problem with your audio configuration"

If this occurs with iTunes 7.0 or 7.0.1, customers may instead see a -200 error when opening iTunes 7.

Products Affected:

QuickTime for Windows, iTunes 7 for Windows, iTunes 8 for Windows

Resolution:

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. Windows XP and Windows 2000: Open the Add or Remove Programs control panel and select QuickTime in the list of currently installed programs.
   Windows Vista: Click Uninstall a program (or alternately, click Programs and Features in Classic View of 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
   
   
   Note: There are two options for downloading QuickTime, be sure to select the second option that does not include iTunes.
5. During the download:
   • If you choose to run the installer, proceed to the next step.
   • If you choose to save the download, double click the QuickTimeInstaller file, then proceed to next step.
6. Follow the on-screen instructions to install QuickTime.
7. Reopen iTunes.

Original site: http://support.apple.com/kb/TS1371