Tony, boehm, if you haven’t touched anything, getting QuickTimeStreaming.qtx back in place should do the trick.
However, if you deleted it, the only thing is to get it from someone, but if you’ve deleted folders and/or uninstalled QT or iTunes I can suggest only what I’ve done as described on my previous message. I can’t say for sure if that will help you too, I’m afraid.
I’ve tried all the suggestions above and nothing will get itunes working again. I’ve spent nearly five hours trying everything I can think of to fix it. All I get on starrting itunes is the Microsoft error message screen. Any help or advice greatly appreciated otherwise I may have to jump out the window. Thanks.