I bumped into a server with ADministrator/[BLANK] account, but when I tryed to log in with TS, or Psexec, it gave me network cannot be found, or access denied when I enter those passwords.. Now, I wish to know how he secured that so I can do the same???

By default win terminal service doesnt allow access when the password is set to blank. To use TS a password needs to b set. Of course altering an admins password will immediately flag the box as being comprimsed

or a honeynet, watch what u scan

paranoia is best policy