itunes bookmarks firefox

Problem with iTunes!?
Ok! So my itunes had a message on it so i had to uninstall and then reinstall, I did this and i got this message, i have gotten this message for a month and i really need Itunes
it gets like 45% done and then it says “error writing file C;Program filesQuicktimeQTSytemQTJNativedll. Verify that you have access to that directory”
What i have tried:
-Uninstalling quicktime and all its folders (all the folders couldnt be deleted)
-Uninstalling, restarting, reinstalling (not working)
-Create a different user on the computer and try to install it (didnt work. same message)
-Delete all cookies and bookmarks off this (firefox) interenet browers
PLEASE HELP ME!
(vista 32 bit)
If you have an anti-virus, then uninstall it until you finish downloading iTunes.
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Tags: iTunes, itunes bookmarks firefox, music, software, tools, web2.0