Restricting account to a computer only

We want to restrict a service account only to login to one computer for
security reasons. 

This is for an exchange 2000 server and obviously we don't want anyone
to use the account/password to read people's emails since the account
must be a member of the Domain Exchange Admin (yeah/neah?). I found an
option under Account / Login To, but it says at the top "This feature
requires the NetBIOS protocol. In Computer Name, type the pre-Windows
2000 computer name". We obviously don't use NetBios, is there any other
way to do this?
To make things even better... The Exchange server is also a DC...... I
didn't do it...

The same concern I have if we create an account and put them in the
Backup Operators group. What can restrict that account to login only on
servera for example and not in all other workstations n the domain?

Thanks so much for your help.

Paul

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