You are an administrator in a company that has Windows 2000 Professional systems. Your users have been installing unsupported USB drivers on to their systems causing them to lock up and fail. You want to insure that only drivers that are in the HAL can be installed. What must be done？（）

• A、Ignore - Install all files， regardless of file signature
• B、Warn - Display a message before installing an unsigned file
• C、Block - Prevent installation of unsigned files
• D、Apply setting as system default