QuickTime crashes at startup and on File Types tab

Question

I have a client who has been trying to install iTunes on Windows XP SP3 32-bit.  The iTunes installation would fail every time towards the end and rollback.  I tracked down Quicktime as the culprit.  Quicktime would crash whenever I tried to launch the player.  When I tried to uninstall the Quicktime already on the system, that uninstall would fail as well.  I used the Windows Installer cleanup tool to remove QuickTime and followed instructions here for removing the leftover QT files from the Program Files and Windows System folders.
I was able to install the latest version of QT, but it then had the same issues, crash when bringing up the player and unable to uninstall again.  I then used Revo Uninstaller which was able to remove QT and all the files and file associations.  After that thorough cleanup, I installed QT again, but with the same results.  I did notice a few things.
I can bring up the QT control panel and switch to any of the tabs except "File Types".  It crashes when I try to select that tab.  The last time I did the install at the final dialog of the installtion it has a button to allow you to set the file types.  When I pushed that button, the installtion did not crash, but you could hear the computer's HD working very hard and nothing ever happened even after 7-8 minutes.  I was able to click the finish button on the installation and the install finished, but I was left with the same crashing problem and inability to uninstall.
The computer is clean of any malware and spyware and I've tried disabling the AV temporarily while doing these installs/uninstalls, but that's no help.
He really wants to get iTunes installed but we can't get past this QT issue.

Answer 1

many thanks.
I think we'd better see if some other application (other than QuickTime itself) has dropped old QuickTime componentry in the system files on the PC. (If there's a version mismatch between the old componentry and the "QuickTime proper" componentry, that can create similar-looking symptoms, including uninstall errors.)
So we'll go looking for the older QuickTime componentry in the most common locations for it to be stashed.
First we'll need to change some view options on the PC.
1. Open My Computer from the desktop or Start menu.
2. In the Tools menu, click Folder Options.
3. Click the View tab.
4. In the "Advanced settings" pane under "Hidden files and folders" make sure that the "Show hidden files and folders" option is selected, and the "Hide extensions for known file types" option is unchecked.
5. Click OK.
Now in My Computer, open your C drive.
Open the "Windows" folder.
Open the "system32" folder.
What files and/or folders can you see in there with QuickTime in the file/folder name? (In a standard installation of QuickTime, you should see precisely two files ... QuickTime.qts and QuickTimeVR.qtx ... and no QuickTime folders whatsoever.)