hardMultiple ChoiceObjective-mapped
220-1201 Practice Question: A technician is troubleshooting a desktop PC that…
A technician is troubleshooting a desktop PC that displays vertical colored lines across the screen immediately after booting. The lines appear even before the operating system loads. What is the most likely cause?
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
✓
The graphics card is failing or has defective video memory.
Vertical lines appearing during POST (pre-OS) indicate a hardware-level issue, most commonly a failing graphics card (GPU) or a damaged video memory. Since the problem occurs before Windows loads, it is not a driver or software issue. Testing with a known-good GPU or reseating the existing one is the recommended step.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
The monitor's refresh rate is set too high in the BIOS.
Why it's wrong here
BIOS settings for monitor refresh rates are exceedingly rare on modern desktop PCs, as display settings are primarily managed by the operating system and graphics driver. Even if such a setting existed and was configured too high, the typical outcome would be a "no signal" message or an "out of range" error displayed by the monitor, leading to a blank screen rather than persistent vertical lines. Vertical lines appearing at boot indicate a fundamental issue with the video signal generation itself, not merely its timing.
- ✗
The video cable is not securely connected to the monitor.
Why it's wrong here
A loose or improperly connected video cable typically manifests as a flickering display, intermittent signal loss, color shifts, or a complete "no signal" message on the monitor. While a severely damaged cable might introduce artifacts, persistent, distinct vertical lines appearing consistently from the moment of boot-up are not the primary symptom of a simple loose connection. Such lines suggest a more fundamental problem with the video signal's integrity before it even leaves the graphics card.
- ✓
The graphics card is failing or has defective video memory.
Why this is correct
Persistent vertical lines appearing immediately upon system startup, even before the operating system loads, are a hallmark symptom of a failing graphics card or defective video memory (VRAM). VRAM is crucial for storing image data and textures that the GPU processes to render the display. Corruption or physical defects within these memory modules, or issues with the GPU itself, can cause incorrect pixel data to be sent to the monitor, resulting in consistent, unvarying vertical lines across the screen. This indicates a hardware-level fault in the video output generation.
- ✗
The operating system's display driver is corrupted.
Why it's wrong here
A corrupted operating system display driver would only affect the display *after* the operating system has begun to load and the driver is initialized. Since the problem of vertical lines appears immediately at boot, often during the BIOS/UEFI POST screen, it precedes the loading of any OS-level drivers. Basic video output during the initial boot sequence relies on the graphics card's firmware and the system's BIOS/UEFI, not the OS display driver. Therefore, driver corruption cannot be the cause of artifacts seen before the OS fully loads.
Go deeper
Related to this question
Learn chapter
Laptop Hardware and Components
Key term
Power-on Self-test
The Power-on Self-test (POST) is a diagnostic process a computer runs immediately when you turn it on to check that essential hardware components are working correctly before loading the operating system.
Key term
POST
Power-On Self-Test (POST) is a diagnostic process that a computer runs when it first powers on to check that essential hardware components are working correctly before loading the operating system.
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JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This 220-1201 practice question is part of Courseiva's free CompTIA certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the 220-1201 exam.