iTunes cannot run because it detects a problem with Quicktime

Download the version of Quickime without iTunes:
http://www.apple.com/quicktime/download/win.html

Now Remove Quicktime using the method for Quicktime in this article (just Quicktime):
XP
http://support.apple.com/kb/HT1925

Vista
http://support.apple.com/kb/HT1923

Since you do not have Quicktime in your list of installed programs, just delete the Quicktime files it recommends, this appears in the final section: +Verify iTunes and related components are completely uninstalled+

When you come to your C:\Windows\system32\ folder you can delete any file or folder with Quicktime in the name.
.
Download and install Microsoft Installer cleanup utility, there are instructions on the page as well as the download. Note that what you download is the installer not the program – you have to run it to install the program. The installer doesn't give any message to confirm the installation.

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

To run the program – All Programs>>Windows Install)

Using the clean up utility, remove any reference you find to Quicktime.

Restart your PC
Then install the standalone Quicktime.

If the Program Files\Quicktime folder is not empty, look inside it.

Try deleting the folders and files in there and there will probably be something in there that you can't delete.

QTTaske.exe can be a problem if it is running. It is the quicktime icon in the system tray.
If that's it open your task manager and find QTTask.exe on the processes tab. Select it and click on "end process". Then try deleting the file again.

If it is something else, get back with the name and location of the file.

If you cannot delete a particular file, first try renaming it. If it is corrupt, Windows may not let you. If so, rename the folder containing the file.

That way the installer will not see the file.

Did you run the disk check? That can sometimes fix problems with corrupt files.

Disk check:
http://windows.microsoft.com/en-us/windows-vista/Check-your-hard-disk-for-errors

When you renamed the problem file or its containg folder, did you rename it to something different so the installer would not find it?

It is very odd that the installer should complain about the SAME file if it was renamed, unless the file it is trying to install is bad and thats seems unlikley.

Glad to hear it worked, I feared that you might have a permission issue which is much harder to sort out. 🙂

Hey. just to let you know that long thing that the other post says to do it total BOLOGNA!!! all you have to do is just download quicktime from apple and it will ask you if you want to "repair" or "uninstall" just click repair. it will do what it has to do then when its finished try opening itunes, it should open perfectly. i just had this problem with my itunes and this worked!