Stik62, this is a function of the permissions structure and the default limitations imposed by Vista. As you may have surmised, you need to take ownership of the file and then you can manipulate it. I found this one of the many annoyances of Vista, but another way to address this is to login as Administrator. While you may think you have all administrative privileges if you have "Administrator" rights, the truth is you don't. Think of Administrator as having Super Administrator rights and you'll be much closer to the truth of what's happening.
By default, the built in Administrator (or root) account doesn't show on the Welcome screen and thus poses a bit of problem for normal users who want to access it. (Hint: MS doesn't want normal users to have access. In a way, I don't blame them, except if they include me!! lol) So, to access that account you need to activate it first.
This you can do in a Command Box (Run... / type "cmd" (no quotes) ). Enter this:
CODE
net user Administrator /active:yes
Now, you will see Administrator on the Welcome screen and you may login. Note there is no password, so you will have to set one once you log in. You can do this in User Accounts as well as through the Management Console.
Hope this helps.