I've been having this error for over a week now. I'm running windows XP and have recently installed a program to help speed up the PC, I believe this program has caused the issue. I have deleted everything asscociated with itunes and reinstalled several times with the same results. I have also tried the Windows Installer Cleanup program and it had no effect either. I would really like to get this back up and running and I'm having no luck, all posts seem to have no answers. Let it be know that I get this error midway through the install of iTunes as well.