I'll post the same thing I posted in another thread; it might help you. Reinstall itunes again according to my post. Some of the information is irrelevant to your problem, but hey, i'm kinda feeling lazy. You'll get the idea. Here it is.....
"this is just a suggestion. If you reinstall itunes again, make sure you follow the directions in the support section of this site for uninstalling itunes and quicktime. Another thing they don't say in that article that I did when i had to uninstall itunes was to do a search. You know, pressing the start button and then "Search". Make sure when you do, click the search "All files and folders". Then set it to look in "Local Hard Drives (C:)" and type in the "all or part of the file name" itunes. After the search is done you should have a bunch of different itunes components in the results. Btw do the same for quicktime as a search. Make sure to DELETE every itunes and quicktime file there. If some of your music files happened to come up in the search use commone sense. Get rid of every component so itunes and quicktime is completely erased from the system. Make sure that you do this after you've restarted your computer once (according to the uninstallation article). Then just empty your recycle bin, reboot your computer, and finally reinstall itunes. Hopefully that will work to at least get rid of that APP error. Good luck and ask me anything you have some questions!!"
Hope that works!
