Hello!
I just downloaded the free version of QT/iTunes to my PC (Windows XP). After trying it for a day, I decided to dump it. I deleted following the normal procedure, add/delete programs. Now when I go to open up files that used to work with WM, it throws up a window that says it needs QT version 5 or higher. It never did that when I only had WM.
I have attempted multiple times to alter program defaults to WM; it never stays there. I have completely removed, to the best of my ability, iTunes and QT. Do the free downloads of QT come with attachments designed to screw windows?
I just want to be free of QT, yet it keeps messing with the movies that have worked with no problem.
Thanks for an insight/ assistance. 
Wow, that sucks. The only solution I can think of is System Restore. I really don’t understand why Windows keeps reverting back to Quicktime as the default player; it makes no sense. I have to say though, this doesn’t surprise me too much considering I have a couple friends who say that Apple software/hardware doesn’t always work as well on Windows when compared to Apple’s own operating systems (I don’t know this firsthand; again, this is just what my friends tell me). Anyways, try a System Restore and see if that helps. Sorry this had to happen to you.