Cannot uninstall QuickTime 7 and getting “Could not open key” error while reinstallation.

I am running Windows Vista in my computer. I had installed Apple QuickTime 7 last month in my PC. Because of some reason I had to uninstall it. Yesterday I reinstalled it in my system, but it wasn’t working. So I again tried to uninstall it from my system but was unable to remove it completely. So again I decided to reinstall it. But this time I was getting “Could not open key” error message. So now basically I still have got those corrupt files. Neither I am able to delete them now I can install a new setup. I am very much confused and hooked up in this problem. Please someone help me to get rid of this problem.

Your problem seems to be very complicated. You have tried uninstallation and reinstallation so much time that I fear you must have spoiled up your registry. I would suggest you to perform System Restore to a restore point when you were not facing any such problems and when QuickTime 7 was working well. Go to: Start > All Programs > Accessories > System Tools > System Restore. Choose the system restore point and click on Next. The computer will perform the rest of the work. Restart your computer when it is prompted.

Do the following steps to uninstall the QuickTime files from your System.

• Quit QuickTime Player if they are running:
• Go to: Start > Control Panel
• When the control Panel starts, click on “Programs and Features.”
• From the list of installed programs, select QuickTime and then, click Uninstall.
• Click yes when asked to confirm the removal of QuickTime.
• Remove all the other entries of QuickTime if you are able to find any.
• Restart your system once you are done with the uninstallation process.

In the majority of cases uninstalling iTunes and its related components from the Control Panel will eliminate all the files related to those programs. In some exceptional case few of those files may be left behind in the system. After following steps mentioned in the above post, you should make sure that the following files and folders are removed from your drive:

• C:\Windows\System32\QuickTime
• C:\Program Files\QuickTime\

Removing the files inside this folder or removing the whole folder will make sure that you have completely uninstalled and removed all the files related to Quicktime. Once you are done with this method just install the version of QuickTime you want to install (If you want to).

Your registry seems to be having some issue after so much or installation and uninstallation process you did in your system. If you not able to uninstall and remove its related components from your system then you should try using some other software, some third party registry utility or software to uninstall any software or application and remove those unused and corrupt links from registry. You can use CCleaner for the same purpose. Search for it on internet and download the setup from its official website and install it in your system. After installation, run CCleaner and uninstall the QuickTime application and also perform registry clean up. This will remove all the instance of QuickTime from your system. Once you done with this, You can perform a fresh install of QuickTime 7 if you wish to.

I am not an expert in this but this solution has helped me when I was facing the same problem and error messages. You should probably backup all you important files and registry before performing the following method:
You should uninstall everything related to Apple and its components, iTunes, OuickTime, Apple Software Updater and every possible thing that has got Apple in its name.
Go to Start > run, type regedit and hit the enter key.
Select “Run as Administrator” option to open the Registry Editor (regedit) Window and go to the following path:
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Installer\UserData\S-1-5-18\Components\DA42BC89BF25F5BD0AF18C3B9B1A1EE8\108B43C0CEA676640B35306AE7D24051

Right click the “DA42BC89BF25F5BD0AF18C3B9B1A1EE8” folder and click on ‘permissions’
Now click on “advanced” button, and then go to the “owner” tab
In the current owners field you must type in “administrators” and tick (check) the checkboxes which will replace the owner and “Apply” the new settings you did.

Again go to the permissions tab and add "administrators" to the permission entries list. Make sure you have checked all the permission boxes, after you click on the edit button. Don’t forget to check the inheritable permissions checkboxes at the bottom of the list. Finally, click OK.
Go to Permissions tab > Administrators (you will find this option in the group or user name window). Here you have to check full control and read checkboxes and finally click on OK.
Now Go to: HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Installer\UserData\S-1-5-18\Components\DA42BC89BF25F5BD0AF18C3B9B1A1EE8 and you will find the keys on the right side pane.
Close the Registry Editor and restart your system.
Finally after restart, download and install the latest available version of quickTime from official site of Apple.