OK,
Double click on "My Computer" then right click on your C: drive and go to properties. Now go to the "Security TAB", now you will see the "Users" that have profiles. You click on one, in the lower pane it will show what permissions they have. You then click edit to check what permissions you want to give, in your case all of them.
You can also do this for folders by right clicking on a folder then to properties, then to Security TAB....
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