My computer has slowed down
Slowness is the most common complaint about a home computer and the one with the longest list of innocent explanations. These six questions work through them in the order that usually pays off, starting with the things that cost nothing to check.
Why has my computer become slow all of a sudden?
Sudden slowness nearly always comes from something that changed recently: a large update installing in the background, a drive that has filled up, a new program that now starts with the computer, or a browser carrying more open tabs and extensions than it used to.
What usually sits behind it
Computers rarely degrade smoothly. They cross thresholds. A system drive that is comfortable at seventy per cent full becomes noticeably sluggish in the last few per cent, because the operating system needs working room for temporary files, paging and updates. A machine with four programs loading at sign-in behaves differently from the same machine with fourteen, each of which checks for its own updates in the first two minutes. And an update that is downloading or installing in the background will slow everything else while it works, then stop.
The word "sudden" is worth examining too. Slowness that arrived overnight points to a change. Slowness that crept up over a year points to accumulation, or to the software you use having grown heavier while the hardware stayed the same.
What to try first, at no cost
- Restart, and let the machine sit for five minutes after it comes back before judging it. Updates often finish in that window.
- Check free space on the drive the system is installed on. If it is below roughly ten per cent, clearing space is the highest-value thing you can do.
- Open the task manager on Windows or Activity Monitor on macOS, sort by processor and then by memory, and see what is actually at the top. One named program is a different problem from everything being equally slow.
- Reduce the startup list to the programs you genuinely want running from the moment you sign in.
- Close the browser completely and reopen it with one tab. If that transforms the machine, the problem is in the browser, not the computer.
When to ask for official help
If the processor is pinned at full load by a process you cannot identify and cannot stop, or if slowness arrived at the same time as files being renamed or inaccessible, stop investigating and get help. The Australian Cyber Security Centre publishes guidance for individuals and a reporting route at cyber.gov.au.
Where a paid product may or may not help
If the cause is a full drive, a heavy startup list or an ageing mechanical disk, no security product will change anything. Where a paid product can help is the narrower case in which unwanted software really is running in the background and the built-in protection has not removed it. That is worth testing before it is worth buying.
Does slow always mean a virus?
No. Slowness on its own is weak evidence of anything. Malware that is written to make money quietly tends to avoid being noticed, and the kind that does slow a machine is usually accompanied by other signs.
What usually sits behind it
The assumption that slow equals infected is old, and it was more reasonable twenty years ago. Modern unwanted software generally wants to stay resident, which means staying quiet. There is one clear exception: programs that use the computer's processor or graphics card for someone else's benefit will make a machine hot, loud and slow, because that is exactly what they are built to do.
A more useful approach is to look for a cluster. One symptom is noise. Three or four together are a signal.
| Pattern | Points towards |
|---|---|
| Slow only, nothing else unusual | Capacity, startup load or ageing hardware |
| Slow plus new pop-ups and a changed search engine | Unwanted browser software, covered on the pop-ups page |
| Slow plus constant full processor load and loud fans with nothing open | A background process worth identifying |
| Slow plus files that will not open and a demand for payment | Possible ransomware; stop and seek help immediately |
| Slow only in one program | That program, its settings or its own updates |
What to try first, at no cost
Run a full scan with the protection already on the machine. On Windows, Microsoft Defender is included and can run a full scan without any purchase. On macOS, the system has its own built-in protections which work without being started manually. A full scan takes time but costs nothing and gives you a clear answer to the question you are actually asking.
When to ask for official help
Files that will not open, a message demanding payment, or evidence that someone else has control of the machine are all matters to report. ReportCyber, accessible through cyber.gov.au, is the national reporting route for cybercrime affecting people in Australia.
Where a paid product may or may not help
A second opinion from a different vendor is occasionally useful when one scanner finds nothing but the behaviour continues. That is a reason to look at a commercial product, and it is one of the uses described on the page about choosing security software.
Why is the fan loud when I am not doing anything?
Because the computer is doing something, even if you are not. Indexing, backups, update downloads and cloud synchronisation all run when the machine looks idle. Heat and dust are the other common explanation.
What usually sits behind it
Operating systems deliberately save their housekeeping for quiet moments. Search indexing rebuilds after a large file move. A cloud folder re-uploads thousands of files after a change. Updates download in the background and then install. All of these raise temperature, and the fan responds to temperature rather than to what you are doing.
Dust is the unglamorous cause. A desktop that has sat on carpet for three years has restricted airflow, which raises temperature, which runs the fan harder and makes the processor slow itself to stay within limits. That produces loud and slow at the same time, which is easily mistaken for an infection.
What to try first, at no cost
- Open the task manager or Activity Monitor while the fan is loud and note the process at the top of the processor column.
- Search for that process name before assuming anything. Most are ordinary system components with unhelpful names.
- Leave the machine on and untouched for an hour. Indexing and synchronisation finish; a mining process does not.
- Check that vents are not blocked and that the machine is not sitting on fabric.
When to ask for official help
If the process at the top is one you cannot account for and it reappears after being stopped, treat it as worth investigating properly rather than guessing. For a machine used for work, your organisation's own support team should be told before anything is removed.
Where a paid product may or may not help
Where the cause is heat, dust or a failing fan, software of any kind is irrelevant and a technician is the right answer. Where the cause is an unwanted program consuming the processor, a scanner is the right tool, and the built-in one is the free place to start.
Why does it take so long to start up?
Because of what loads with it. Startup time is mostly determined by the number of programs that have been given permission to launch at sign-in, and by whether the system sits on a mechanical drive or a solid-state one.
What usually sits behind it
Almost every program installed over the years asks to start with the computer, and most people click through that question. Printer utilities, music players, chat clients, game launchers and updaters each add a few seconds and a share of memory. None of them is harmful. Together they can double the time between pressing the power button and being able to work.
Drive type matters more than anything else. A computer still running its operating system from a spinning mechanical drive will feel slow at startup no matter how clean the startup list is, because that is the limit of the hardware.
What to try first, at no cost
- On Windows, open Task Manager and look at the Startup tab, which lists each item and an estimate of its impact.
- On macOS, look under System Settings at the login items for your user account.
- Disable rather than uninstall. A disabled item can be switched back on in a moment if you find you needed it.
- Change one group at a time and restart, so you know what made the difference.
- Leave security software and drivers alone. These are the items that should start with the machine.
What to watch out for
Programs that promise to optimise startup automatically are a mixed category. Some are legitimate; some are the "potentially unwanted programs" that security vendors classify separately, which is to say they were installed alongside something else and are more interested in selling you an upgrade than in saving you four seconds. The startup list is short enough to read yourself.
When to ask for official help
If an item in the startup list cannot be disabled, returns after every restart, and has a name that matches nothing you installed, that is persistence, and it is worth proper help rather than repeated attempts.
Where a paid product may or may not help
Trimming a startup list needs no purchase. A commercial security product becomes relevant only if the stubborn item turns out to be unwanted software that the built-in tools will not shift.
Is my computer simply too old now?
Age alone does not decide it. What decides it is whether the manufacturer still issues security updates for the operating system, and whether the hardware can run the software you actually need.
What usually sits behind it
There are two separate questions hiding inside "too old". The first is performance: an eight-year-old machine with a solid-state drive and enough memory can be perfectly pleasant for email, documents and video. The second is support: once a version of Windows or macOS stops receiving security updates, newly discovered weaknesses in it are never fixed, and no antivirus product replaces that. Microsoft and Apple each publish their own support timelines, and those pages are the only reliable source for the dates.
The second question is the one that should drive a decision. An unsupported system is a different situation from a slow one.
What to try first, at no cost
- Find which version of the operating system the machine is running, and check the vendor's own support page for whether it still receives updates.
- Check whether a free upgrade to a still-supported version is offered for your model.
- If the machine is slow but supported, measure where the limit is: memory pressure, disk activity or processor load.
- Consider what the machine is used for. A browser and documents ask far less than video editing or recent games.
When to ask for official help
The manufacturer's support channel is the right place for questions about whether a specific model can take a newer operating system. For general advice on keeping devices up to date, the Australian Cyber Security Centre's guidance for individuals and families at cyber.gov.au covers the principle without being tied to one vendor.
Where a paid product may or may not help
Buying security software for a computer whose operating system no longer receives updates is treating the smaller problem. The sequence that makes sense is: get onto a supported system first, then decide what protection to run on it.
Do the clean-up and speed-up tools help?
Some do a little; the ones advertised most aggressively tend to do least. Almost everything a clean-up tool does is available in the operating system without installing anything.
What usually sits behind it
The category is crowded because the promise is appealing. In practice, deleting temporary files, emptying caches and removing unused programs are all built into Windows and macOS, and the gains from doing them are modest unless the drive was nearly full. Tools that advertise registry cleaning on Windows are offering to tidy something that is not usually the cause of slowness.
The real risk is the business model. Free clean-up tools often make their money by reporting a large number of "issues" and asking for payment to fix them, or by changing browser settings as part of installation. That is the behaviour described on the page about toolbars you did not install.
What to try first, at no cost
- Use the storage management built into the operating system to see what is taking space and to clear temporary files.
- Uninstall programs you no longer use through the system's own program list.
- Empty the recycle bin or trash, and check the downloads folder, which is often the largest single surprise.
- Move photos and videos you want to keep onto an external drive or a cloud service.
A note on claims
Advertising that promises a specific percentage improvement in speed is making a measurable claim about your particular machine, which it has not measured. Under the Australian Consumer Law, misleading claims of that kind are a matter for the Australian Competition and Consumer Commission, at accc.gov.au.
When to ask for official help
If a clean-up program will not uninstall, or demands payment to undo changes it made, that is worth reporting to Scamwatch at scamwatch.gov.au as well as removing.
Where a paid product may or may not help
A mainstream antivirus product is a different category from a clean-up utility, and the two should not be confused. Norton AntiVirus Plus is an antivirus product for desktop computers; it is not a performance tool, and a slow machine with no other symptoms is not the problem it addresses.
Visit the Norton AntiVirus Plus websitePaid affiliate link. Mildfactor is paid a commission if a purchase follows this link; your price is unchanged.