220-1101 Hardware and Network Troubleshooting Practice Question
A technician is troubleshooting a desktop computer that fails to boot and displays the error message 'Boot device not found'. The technician has verified that the hard drive is detected in the BIOS and that the boot order is set correctly. The hard drive is spinning and appears to be receiving power. Which of the following is the MOST likely cause of this issue?
⚠ Common exam trap
Candidates often assume a detected drive means the boot data is intact, but the BIOS detecting the drive only confirms the hardware interface works, not that the boot sector is valid.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
A. Corrupted MBR/GPT
Since the hard drive is detected in BIOS, spinning, and receiving power, the issue is not a hardware connection or power failure. The 'Boot device not found' error with correct boot order indicates that the bootloader (MBR or GPT) is corrupted or missing, preventing the system from reading the boot sector to load the operating system.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
A. Corrupted MBR/GPT
Why this is correct
A corrupted Master Boot Record (MBR) or GUID Partition Table (GPT) does not affect the drive's physical detection by BIOS/UEFI, but it does erase the metadata needed to locate and execute the bootloader. This is why the system initially sees the drive, yet reports that no bootable device exists when attempting handoff. The boot sector or partition table being overwritten by bad sectors, virus activity, or an interrupted write is a classic software-level cause that matches a drive-detected-but-unbootable symptom exactly.
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B. Bad SATA cable
Why it's wrong here
A bad SATA cable normally causes the drive to vanish from the BIOS boot list, fail to spin up, or suffer intermittent disconnects during POST. Since the system clearly detects and identifies the drive before attempting to boot, the cable's data and power paths are delivering the drive's identity and capacity correctly. A failed cable would not produce a clean 'boot device not found' message without also triggering drive-detection warnings or disappearing hardware.
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C. Failing power supply
Why it's wrong here
A failing power supply typically reveals itself through the system failing to POST, random reboots under load, or components not receiving enough power to initialize. The fact that the machine has progressed all the way to drive detection and boot-device enumeration demonstrates that the CPU, RAM, and storage are being powered and responding; a PSU insufficient to support these processes would crash the system far earlier. While an unstable PSU could theoretically corrupt data, it does not straightforwardly generate a controlled 'no boot device' error when the drive is otherwise detected.
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D. Loose RAM module
Why it's wrong here
Loose or faulty RAM typically interrupts the POST routine before the firmware can configure storage interfaces, producing a blank screen, no video signal, or a series of beep codes. Because the system has already executed firmware routines, initialized the SATA controller, enumerated the drives, and reached the boot-device selection stage, the memory is demonstrably functional enough to run the firmware. If a RAM module were loose, the process would halt during memory counting or the early hardware check, not at the boot-loading step.
Go deeper
Related to this question
Learn chapter
BIOS and UEFI Settings
Key term
Operating system
An operating system (OS) is the core software that manages a computer's hardware and software resources, providing common services for computer programs.
Key term
MBR
MBR is a 512-byte boot sector that stores partition table and boot code, enabling a computer to load an operating system.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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