On my Windows 7 x64 system the QTMovieWin.dll file is in the folder E:\Program Files (x86)\Common Files\Apple\Internet Services. On someone else's system, this might more likely be C:\Program Files (x86)\Common Files\Apple\Internet Services. However, adding this folder to the system Path did NOT fix my problem. iTunes continues to crash on attempting to access the iTunes store. My problem IS identical to that reported in this thread, down to the same displacement within the WebKit module.
I also tried coping the QTMovieWin.dll file to the folder containing iTunes.exe. Doing so caused another sort of error on program launch. I infer that QTMovieWin.dll IS being access by iTunes.exe, exactly as claimed in this thread. However, other files in the same folder are also accessed so it's important to modify the Path as directed rather than merely copy a file or two. I infer that, in the case of Windows 7 x64, the suggested fix may not be quite right. At least, I suppose that's the reason it failed in my case. Further experiments pending. I'll report anything that works or looks promising.