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Power-on Issues: Desktop-Computer Troubleshooting Guide

Dan received the CompTIA IT Operations Specialist (cert.) in 2010 and worked in the computer repair/networking industry for several years.


Everybody needs assistance with computer problems on occasion. Because of the many shapes and forms of tech problems, however, it can be difficult to write a comprehensive help guide.

This article focuses on startup issues related to desktop computers. It’s not intended to be a complete list of problems and solutions. It should be used more like a guide for the most common faults related to startup problems — assuming that only one operating system is installed.

Whether the operating system installed is Microsoft Windows, macOS or Linux there are common steps that can be taken to resolve startup problems. It should be noted, however, that while the tips listed herein are simple they're not always feasible to apply without assistance.

Quick Notes Before Proceeding

If a computer is shutting down during the startup process, it’s probably due to its CPU overheating. Please research computer-cooling issues and solutions via the internet. I don't discuss them here.

Certain conventional terms in this article are in italics and can be searched on the internet for precise definitions. They're also found in books.

The Power Button

Between the time of pushing the power button and when the home screen is visible, the computer goes through a series of phases and each has characteristics. Certain audio cues called beep codes will sound in the early stage of startup if there are major hardware problems. The sounds help with troubleshooting.

In some cases, the beep codes are manufacturer-specific but there can be an overlap between makers' standards. Consult manufacturer documentation for specific beep code meanings.

Troubleshooting Power Problems

  • If pressing the power button and nothing appears on the screen, it could be due to a loose monitor cable, accidental unplugging, a faulty electrical receptacle, a tripped breaker or deactivation of a power stripe. Check the said possible culprits.
  • When the power button is pressed, one or more LED lights and cooling fans should turn on indicating that the computer is generally receiving power. When light and fan activity is absent, it indicates a power problem. If possible, remove the side cover of the computer and check for fan activity — listening for fan noise can also work.
  • The next power-problem culprit that should be checked is the computer power supply. An inexpensive voltmeter can be used to check the power supply pin voltages. The 5-volt DC pins should register within +/- 5%. The 3-volt DC pins should register within +/- 5%. The 12-volt DC pins should register within +/- 5%. Search Google for more-detailed steps on this method. Alternatively, a faulty power supply can be determined by swapping it with one sufficient in wattage and known to be working. If the computer powers on with a different power supply installed, it can be concluded that the problem was a faulty power supply.
  • A faulty computer motherboard can inhibit different parts of a computer from receiving power. When all other power-problem culprits are ruled out, the motherboard needs to be replaced. Generally, motherboards are not repaired, they are replaced. Repairing them is generally uneconomical.

Beyond Power Issues

When a computer is powered on, the first phase it goes through is what’s called a POST or power-on-self-test. Built-in software (on the motherboard) checks to make sure certain hardware is working.

POST Detections

If the POST detects hardware issues, details will be displayed on the attached monitor. The test can also signal with a beep code. A particular beep sound indicates what's wrong — the beep code can be referenced in the computer manufacturer's documentation. If no hardware issues are detected, the manufacturer logo splash screen will appear, implying the POST is completed. The boot process will then continue.

POST Failure

Sometimes POST will not complete, rendering a blank screen and no beeps. If this is the case, reseating power supply cables, peripheral devices and RAM-memory modules might resolve the issue. Sometimes connections need to be tightened.

Power supplies on the brink of failure can also cause the POST check to stall. If possible, check the power supply and then move on to checking RAM.

Scroll to Continue

Removing the suspect RAM module and rebooting the computer can reveal which module is causing the problem. If there is only one module installed, however, the only option is to swap it with one that is compatible and known to be working.

If purchasing a new module, be sure to get the type that is right for the computer. DDR3 and DDR4 are the most common at this time. DDR1 and DDR2 are becoming phased out although they can be found in computers owned by hobbyists. The modules can be removed for gleaning technical specifications. Be sure the purchased module has the right speed capability which should be greater than or equal to that of the original module.

A failing motherboard can cause the POST check to fail. If ruling out the said components is done, the motherboard is likely the culprit.

Continuing the Startup Process

After POST has been completed, the built-in software called the BIOS passes control of the startup process to the primary data-storage drive where the operating system (e.g., Microsoft Windows) is installed. Depending on the partitioning scheme on the drive (which can be customized), a couple of different things can happen.

Assuming they are working, the MBR (master boot record) or GPT (GUID partition table), located in a tiny section of the drive, will point to the partition where the operating system is installed. Then, the operating system will be loaded.

If failed, some of the visuals on the screen will be a stalled or slowed startup process, stop/blue screen errors, "missing drive" and other possibilities. Possible culprits to consider are a failing hard drive (or drive cable), loose drive cable, failing RAM memory, failing power supply, corrupted file system, corrupted operating system files, too many startup programs trying to load or malicious software (viruses or spyware). If your computer boots up to the point where it appears to be making progress (although slow), check the culprits mentioned up to this point before moving on. Troubleshooting some of these will be discussed further down in "Advanced Troubleshooting."

  • If the computer can be booted into safe mode, it will rule out hardware problems. Safe mode runs a slimmed-down version of the operating system and disables most programs. Another benefit of safe mode is that files can be recovered if repair is not feasible at the time.
  • To boot into safe mode in Microsoft Windows, start by shutting off the computer. Power it back on and instantly tap the F8 key until the safe mode boot options appear. If an internet connection is needed while in safe mode, select “safe mode with networking,” otherwise select “safe mode.” If the computer is sufficiently working, another way of accessing safe mode is by typing msconfig into the RUN-command app in Windows, selecting the boot tab, checking the boot box, adding the network support bubble and rebooting.

Hard Drive Troubleshooting

  • To rule out a failing hard drive, it can save time by making sure the computer’s BIOS recognizes the device. Follow the manufacturer’s guide for entering the computer’s CMOS setup program. Once the CMOS set-up program is on screen, look at the “Main” tab. The make/model of the storage device or hard drive should be listed along with how many bytes of data it can hold.
  • If the device is missing in the “Main” tab, the hard drive has likely gone bad and needs to be replaced. Though, the drive cable might simply need to be replaced or reseated.
  • If the drive is showing in the computer’s CMOS settings, troubleshooting it further can be done. Software tools downloaded from manufacturers or third parties can be used for this purpose. Instructions for using the software are typically displayed on manufacturer sites.

Advanced Troubleshooting

Even though hard drives are recognized (as indicated above), sometimes their individual memory locations, also called sectors and blocks, can go bad. Checking for them can be necessary.

If there are mission-critical files stored on the computer, however, a best practice is to consult with a data recovery expert to determine the cost of recovery. Attempting to scan hard drives can advance damage and render subsequent data recovery attempts impossible.

  • Using a working computer, install the scanning software (downloaded from the manufacturer or third party) to a bootable USB drive. Plug the USB device into the problematic computer and power it on for scanning the hard drive. If bad sectors or blocks are found, drive replacement should commence which implies an eventual reinstallation of the operating system.

Once faulty hard drive sectors/blocks are ruled out, other culprits that can produce onscreen symptoms must be ruled out. The same troubleshooting software (typically a multi-featured program) can be used to test RAM memory, check for a corrupted file system and repair/replace corrupted operating system files.

Installed software can also cause startup problems. Operating systems have ways to limit which programs start when a computer is powered on. Consult the procedure available for the operating system installed. Searching on Google for "currently-installed operating system + disabling startup programs" will work.

Malicious software can be ruled out or fixed by following recommended procedures for the given symptoms and situation. There are several guides available on the internet for virus removal. Check my portfolio for the Microsoft Windows virus removal guide.

Power It Up!

This guide is generally applicable to the three mentioned operating systems. The procedures and features discussed herein will look different onscreen depending on which operating system is being used. If necessary, search the internet for more details about some of the keywords mentioned.

Laptops can also be repaired by following the steps listed in this guide, although troubleshooting power problems in them will be different — since they're powered by chargers and batteries. For common run-time problems with desktop/laptop computers, my performance guide can be referenced from my portfolio.

This content is accurate and true to the best of the author’s knowledge and is not meant to substitute for formal and individualized advice from a qualified professional.

© 2022 Dan Martino

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