A companys computers are running Windows XP Professional. Some of the desktop computers have the file ntbootdd.sys on the root but it is not seen on any laptops. The ntbootdd.sys file is required for：（）

A.Back up all important documents. 
B.Set a System Restore point. 
C.Note the BIOS settings in case a reset is needed. 
D.Back up the drivers for the computer in case re-installation is needed. 
E.Uninstall the previous service pack.

A.Start > Run > MCP
B.Start > Run > MCE
C.Start > Run > MCA
D.Start > Run > MMC

A.Control Panel Administrative tools.
B.Control Panel Security Center.
C.System Properties， Start up and Recovery.
D.Help and support from the Start menu.