Just a few things that may help in future when dealing with permissions.
Permissions are applied to the actual files and not the Operating system, what this means is that they are written to each file and folder individually and will survive the re-install of an OS or the installation of another OS
Permissions in windows are set to automatically cascade through the folder tree when applied. This results in any permission changes applied to a folder will attempt to be applied to all files and sub folders in the segment of the file tree concerned. It also means that to change or remove permissions it is often required to go up the folder tree to the point where there original permissions were added, although it is often possible to add extra permissions at the point you wish.
When running an administrator account in Windows 7 (or Vista), you actually run as a standard user, if UAC is on.
In order to change permissions you actually have to have a specific permission set for your user on the folders or files, Due to the dual nature of the normal administrator group accounts in win7, (or vista), it is possible that the standard form of the user account will not have this permission whilst the elevated user will.
This permission is part of the full control permissions and is also automatically granted to the owner of the folder or file.
Switching UAC off will automatically elevate the user status, as will running in safe mode, or running as the hidden system administrator.
When cascading the applied permissions down the folder tree it is possible that the system will encounter folders where the user applying the permissions does not have the required Change file permissions Permission, this will cause Windows to produce an error. In these situations it will be necessary to go to the folder and add the correct permissions.
There are various advanced options to control the application of permissions which can break the link between the current folder and it's parent, that may be useful at times.
Basically the application of NTFS file permissions is a complex one that is made more complex by the UAC in Win7 so unless you are certain of the consequences is best to leave well alone. Saying this, the control that the correct use of permissions can provide in a network or multi-user scenario is well worth the effort of learning how they work