单项选择题 A workstation has an error message that states “NTLDR is missing”. Which of the following is MOST likely the cause?（）

单项选择题 A technician is replacing a processor in a workstation. After installation, the workstation starts up and immediately shuts down; the technician tries to start the workstation several more times and gets the same result. Which of the following is the cause of this issue?（）

单项选择题 A technician upgrades a computer from Windows XP Media Center Edition to Windows Vista Home Premium. After the upgrade Aero will not turn on. The system has a 2.4 GHz processor, 1GB of RAM, and a DirectX 7 video card. Which of the following will resolve this issue?（）