A user reports that the Windows update function will not run on the computer but the Internet can be accessed. The user is running an original version of Windows XP Professional. Which of the following is MOST likely the cause？（）

A.The user has not registered the copy of Windows.
B.The user has not applied at least Service Pack 1 to their system.
C.The user does not know what site to access for the updates.
D.The user needs to flush the DNS cache.