First have you tried to un-install QT? If so, have you deleted the temp folder that it was in?
I saw part of this thread b4. I dont know if anyone sugessted it but Have you gone to C:\users\richard\.... temp\quicktime.msi and deleted all the files.
It might be an entry in registry for quicktime that is corrupted or keeps installing into the same temp file directory. I dont know how comfortable you are with editing the registry but BE CAREFUL. Backup first.
There are also apps that remove all traces of an un-installable application. I had a poorly written app I couldn't get rid of.
I hope some of these suggestion haven't been discussed or tried before
Hope I helped