When you're logged in using a “Computer Administrator” account, you have permission to change any aspect of Windows, including any file, folder, or user account. This is exactly what you need when you're installing new hardware or software, managing user accounts, setting permissions on folders, or performing other system management tasks.
However, this carte blanche power is overkill for day-to-day work. While it may seem convenient, using the Administrator account poses several risks:
You might inadvertently delete a crucial file needed for system operation.
You might accidentally receive an email virus, or visit a Web page that has malicious script code embedded inside. Run from the context of an Administrator user ...