Windows

What you ask for is a little bit strange - once the administrator has no rights to the specific folder, if something is crashed or lost, then I suppose, you don't blame the administrator for the situation!! Any administrator has the right to "take Ownership" on every folder that resides on the partition of a server, but what I suggest you is to do the followings:
- add an AUDIT on access to the folders you want. Give rights to the manager or anyone else to access the audit logs. This way you/he'll be informed on every step that each user did to the folders.
I suppose you are asking this because you don't trust the administrator, otherwise I don't get your point.

Even if this were possible (which I don't think it is), I don't know ANY Admin who would allow this.
A Network Admin MUST be considered in the same priviledged class as Security Admins and System Programmers on a mainframe! In order to maintain the systems AND fix problems, they MUST have access to everything.
If you can't trust your Admin, its time to get a new Admin rather than trying bar access.

Ralph

You can kind of do this by adjusting the options under the security tab to not allow Administrators access to this folder. However, as an Administrator, someone could take ownership, and then reassign permissions so they can see the folders. It is not possible to truly lock the Admin out of the folder, but you can make their life more difficult.

If you really don't want this person to have access, then you shouldn't give them an Administrator account...

In summary (as all these answers are correct as far as they go), the short answer is no, you cannot totally lock out the Administrator.

As you surmise, you CAN set permissions to exclude the Administrator. However, the owner of a file/folder can always modify the permissions of that file/folder. And the Administrator can ALWAYS "Take ownership" of ANY file/folder.

If there are sensitive files you don't want the administrator to see, you should consider encryption.

If you don't trust your Administrator to not go where you tell him not to go, he shouldn't be your Administrator.

The point is not whether I would want him/her looking at sensitive info. The point is I MUST be able to trust him/her NOT to even though he/she CAN.

Again, if you can't trust your Admin, get a new Admin. Don't try to lock him/her out because you CAN'T.

Ralph