iTunes / QuickTime install problem

I have a new Dell XPS laptop with Win XP Pro SP2 that I cannot get iTunes and QuickTime installed on. The install process appears to complete OK, but when you try to run iTunes, you get an error windows that says iTunes has encountered an error and needs to close. When you try to run QuickTime, nothing happens except that you get an hourglass with the cursor for a second or two. Uninstalling and reinstalling does not work. iTunes will uninstall, but the QuickTIme uninstall appears to complete only to report an error when you click on Finish. The Windows Installer Cleanup Utility has been used, but that has not helped either. Any ideas as to what to try next would be appreciated. Thanks.

Did you disable your antivirus?
Some will cause that.

I disabled McAfee as far as is possible. McAfee does not actually have a way to disable it built in that I can find. Closing the system tray icon doesn't really do anything, and you can't End Task some of the McAfee items without locking up the PC.

At one time, you could do that in msconfig.

One of the reasons I gave up on McCaffee years and years ago was the pain it gave me when I went to do a install.

Update:

After uninstalling QuickTime and iTunes and removing all files from Program Files, and Windows folders, then deleting all registry entries for iTunes and QuickTime, the installation was successful.

Thanks for posting the fix.