The Contacts entries aren't stored in a separate file. They're stored along with the Calendar, mail folders, task list, and all the other Outlook folders in a single Personal Folders (.pst) file.
The .pst file is unique for each Outlook user profile, and is set up when the user is initially set up.
The following procedure can be used to identify the file name of a Personal Folders file in Access 2000:
1. Display the Outlook bar if it's hidden.
2. Right click the Outlook Today button.
3. Choose Properties from the context menu.
4. In the Properties dialog, click the Advanced button.
5. Copy the .pst file path from the Path text box.
Note: This procedure gets you the user's main .pst file, the one normally accessed by the buttons in the Outlook bar. It's possible for a user to create or attach multiple .pst files. If they do this, each .pst file's set of folders will appear in the Folder List (View>Folder List). You can right-click the root folder of each set to display its properties and get each file name.