Deny log on locally

There must be an administrator profile on the PC. But you can create a password for both yourself and administrator. Then only you can access the PC.

Well there are a wealth of things you can do, though am not sure if you logon locally or through the net. either way, I'll point you to where you can play around with user rights:

Clcik Start->Run
in the run dialog box, type gpedit.msc
when in the group policy editor, navigate to:
Computer Configuration->windows settings->Security Settings->Local policies->User rights assignments.

you can then read through the vast options to deny logons, allow logons....well, you choose what to do while there. Note that these changes are local to the computer. In that same hive, after 'local policies', you can choose 'Security Options' and select to rename the Administrator account, that's the only work around I can think of. You could make it your user name, though you know it's not wise to keep logging on as Admin.

You can disable the administrator account by right clicking < my computer > choose "manage" This will open < Computer Management > expand "Local Users and groups" Choose "Users". Double click administrator and chechmark the box for "Account is Disabled".