cannot reinstall itunes, cannot uninstall previous version

I need to uninstall itunes as suggested so I can install windows 7, but all if it will not uninstall... I get a message that the old itunes cannot be removed. I removed everything as per itunes uninstall instructions, but this one file will not be removed. I keep getting the message "The feature you are trying to use is on a network resource that is unavailable" and "the installation source for this product is not available.. verify that the source exists and that you can access it" I have searched the entire computer for other itunes files including itunes.msi which seems to be the missing file. To no avial. So I cannot reinstall itunes!! (still using Vista have not put windows 7 in yet waiting for a bit so I wanted itunes back in my computer) How do I get rid of this last file?