Can't upgrade Itunes

I have itunes 7.1 want to upgrade to 7.7 - During installation I get the following message (HKEY_LOCAL_MACHINE\SOFTWARE\MozillaPlugins\@apple.com/itunes,version= Check to make sure you have access). I finish and the installation rolls back and I am sutck with the old version. Then when I try to open the old version I get the following error (itunes was not properly installed, if you want to retrieve cd info from the internet you need to reinstall itunes). Any ideas? I am aware that this is a registry key situation. Any help is appreciated.