Computers give signals before they fail. Not always obvious ones — and sometimes the signals are misleading — but a machine that's developing a hardware fault or heading towards a significant failure usually shows some signs beforehand. Knowing what to look for isn't about being technically minded; it's about paying attention to changes in how the machine behaves.
This article outlines the most common symptoms we see, what they typically indicate, and when it's worth getting a professional opinion versus attempting to address things yourself.
One important caveat: symptoms rarely point unambiguously to a single cause. A slow computer might have a software problem, a failing drive, insufficient RAM, overheating, or several of these in combination. The purpose of this guide is to help you decide whether something warrants professional attention — not to provide a definitive diagnosis.
Performance-related symptoms
Gradual slowdown over months
A computer that has become noticeably slower over a period of months — longer boot times, sluggish application loading, delays in basic tasks — is one of the most common situations we see. It's also one of the most ambiguous, because the cause could be almost anything.
Software factors are the most common explanation: accumulated startup entries, background processes, a nearly full SSD, operating system files that have accumulated issues, or malware. These are generally resolvable without hardware replacement.
Hardware factors include a failing storage drive (SMART errors often precede noticeable performance degradation), insufficient RAM for current workloads, or thermal throttling caused by dust accumulation in the cooling system. The latter is worth considering if the slowdown is more pronounced during demanding tasks and the machine also runs hot or the fans are noticeably louder than they used to be.
A useful test: if basic tasks like opening a browser or a document are sluggish but the machine speeds up noticeably after a restart, this often points to a software or memory management issue rather than hardware. If performance is consistently poor regardless of recent activity, hardware factors are more likely.
Sudden, dramatic slowdown
A machine that was working normally yesterday and is now very slow today warrants more urgent attention than gradual degradation. Possible causes include a failing storage drive (particularly if it's an HDD with read errors), the early stages of a malware infection, a Windows Update that went wrong, or a hardware fault that has partially disabled a component.
If the sudden slowdown is accompanied by unusual disk activity (the drive indicator light on a desktop staying on continuously, a laptop that's unusually warm on the base), this strengthens the case for storage drive issues.
Freezing and unresponsiveness
Occasional, brief freezes followed by recovery are often software-related — a background process hogging CPU time, a temporary disk I/O bottleneck, or a poorly coded application. Frequent, prolonged freezes that require a hard reset are more concerning.
RAM faults are a common cause of freezing and system instability. A simple memtest (running overnight) can often identify faulty memory. Storage drive issues can also cause freezing, particularly if the system is waiting on a read or write that the drive is struggling to complete.
Boot and startup symptoms
The machine won't turn on
A computer that shows no signs of life at all — no fans, no lights, no display — when the power button is pressed could have a failed power supply, a faulty power cable, an issue with the motherboard, or (for laptops) a dead battery and a faulty charging circuit.
Before assuming the worst, check the obvious: the power cable is properly seated, the surge protector (if present) is on, and for desktops, the power switch on the rear of the PSU is in the on position. These account for more "dead computer" calls than you might expect.
If the machine powers on briefly — fans spin for a second, then everything stops — this is often a power supply fault or a short circuit somewhere in the system. If the machine powers on but doesn't display anything (no POST screen, no boot), the fault lies somewhere in the POST sequence: RAM, GPU, storage, or motherboard.
Intermittent startup failures
A computer that sometimes boots normally and sometimes doesn't is one of the more frustrating diagnostic scenarios, because the fault is by definition difficult to reproduce consistently. Common causes include a failing CMOS battery (which can cause BIOS settings to reset and confuse the boot process), a storage drive with read errors that sometimes affects the boot files, or loose connections — particularly in desktop systems where vibration can gradually work components loose.
Thermal and audio symptoms
Overheating and unexpected shutdowns
Computers are designed to shut down when they reach a thermal limit, to prevent damage. If your machine shuts down during demanding tasks — gaming, video editing, or even sustained web browsing on older hardware — thermal throttling or shutdown is a likely cause.
This is usually fixable. The most common cause is accumulated dust in the cooling system, which is addressed through internal cleaning and, if the thermal paste has dried out, its replacement. Fan failure is another possibility — a fan that's running slowly or has stopped entirely will significantly reduce cooling capacity.
Persistent overheating after cleaning may indicate that the system's cooling capacity is simply inadequate for its workload, that the thermal solution needs upgrading, or (in some cases) that there's a hardware fault causing abnormally high power consumption.
Unusual sounds from inside the machine
Computers should be relatively quiet. The sounds you'd normally hear are fans (a consistent, low hum that increases under load) and, for HDDs, the gentle whir of the spinning platters. Anything outside this baseline is worth investigating.
Clicking or ticking sounds from a hard drive are a serious warning sign. This is often described as the "click of death" — the read/write head repeatedly failing to find its target track. A drive making this sound is at significant risk of imminent failure, and any data on it should be backed up immediately if it's still accessible.
Grinding sounds typically come from a failing bearing — either in a fan or, more seriously, in a hard drive. A fan with a failing bearing will usually continue to operate for a while before failing, giving some warning time. A grinding hard drive is in a worse position.
Rattling or vibrating sounds are often less serious — a screw that's come loose inside the case, a cable lying against a fan blade, or a panel that's not properly seated. These should still be investigated, but they're rarely indicative of component failure.
Display and visual symptoms
Screen issues on laptops
Laptop screen problems fall broadly into three categories: physical damage (cracked or shattered panel, which is visually obvious); backlight failure (the screen appears dark or very dim, but you can faintly see content if you look closely); and signal or connector issues (flickering, random lines, partial display, or colour distortion).
If the screen works correctly when connected to an external monitor, the fault is in the laptop's display system — likely the panel itself, the cable connecting it to the motherboard, or the connector. If the external monitor also shows problems, the issue is in the GPU or the graphics subsystem.
Artefacts, flickering, and display anomalies on desktops
Visual artefacts — random pixels of incorrect colour, geometric patterns, corrupted rendering — on a desktop display can indicate a GPU fault, a failing display cable, or an issue with the monitor itself. Testing with a different cable and, where possible, a different monitor helps narrow this down.
Flickering that occurs at certain refresh rates or when the display moves may be a cable issue; artefacts that appear under load (during gaming, for example) are more likely GPU-related.
When to seek professional help
The general principle is: the more persistent, progressive, or disruptive the symptom, the more it warrants professional attention. A computer that occasionally stutters is worth monitoring; one that crashes daily is affecting your productivity and potentially putting your data at risk.
Data is the deciding factor that should accelerate the timeline in many cases. If a symptom might indicate storage drive failure — unusual drive noises, SMART errors, slow file access, the machine not recognising the drive — the priority is to get your data off the drive while you still can. This should happen before the machine goes in for repair, if at all possible.
If you're unsure whether a symptom warrants attention, describe it to us. We'd rather have a brief conversation that reassures you than have you wait until a minor issue becomes a major one.
We don't charge for initial conversations or basic assessments of whether a repair is likely to be worthwhile. Get in touch and tell us what's happening — we'll give you an honest view.