In order to turn off or disable the "My Site" or "My Links" functionality you need to be a SharePoint Administrator. Then follow the steps below.

• Go to the Central Administration Web Page
• Click on the link for Shared Services Administration
  • If you have more than one Shared Service Provider (SSP), select the one that is running the "My Sites" functionality
  • Under "User Profiles and My Sites", click "Personalization Services Permissions"
• Select the group you want to limit the functionality.  More than likely you will just have "NTAuthority\Authenticated Users"
• Click Modify Permissions of Selected Users
• In the next screen, you will see a list of checkboxes
  • To disable "My Sites" uncheck "Create Personal Site"
  • To disable "My Links" uncheck "Use Personal Features"
• Select the checkbox that is appropriate for you