My computer has slowed down

Seven questions about a computer that is not as quick as it used to be, answered without assuming the cause is malicious. In most households it is not.

My computer became slow this week. Is that a virus?

Almost certainly not. Slowness that appears over days is far more often the result of something routine: an update downloading in the background, a disk that has filled up, or a browser that has quietly accumulated work to do.

Likely causes. A major operating system update installing itself over several restarts. A cloud drive performing its first full sync. A photo application rebuilding a library index. A drive with only a few gigabytes free. A laptop running hot and reducing its own speed to cope. Any of these can halve a machine's responsiveness for a week.

What to try first, at no cost. Restart and leave the computer on, plugged in, for half an hour without touching it, so paused installations finish. Check how much space is free on the system drive. Then open Task Manager on Windows or Activity Monitor on macOS, sort by processor use, and read the name at the top — if it is an update service, a backup tool or a browser, you have your answer.

When to ask for official help. If the computer belongs to an employer, ask their IT contact first, because managed machines run background tasks you are not meant to disable. The Australian Cyber Security Centre publishes general guidance for individuals and families at cyber.gov.au.

Where a paid product may or may not help. If the machine is still behaving oddly after all of the above — programs you did not install, a browser that resets its own settings — a scan is a reasonable next step. If the answer was a full disk or a pending update, security software will not change anything.

Why is the fan loud even when I am not doing anything?

Because something is working, or because heat is not escaping. A fan responds to temperature, and temperature responds either to load or to airflow.

Likely causes. Dust in the vents, which builds up over two or three years, especially in a house with carpet or pets. A laptop used on a bed, where the intake is covered. A background task such as indexing or a scheduled backup. A browser tab playing video, which can occupy a processor core indefinitely. Ambient temperature matters too: a machine that is quiet in July may be loud in a Queensland February.

What to try first, at no cost. Put the laptop on a hard, flat surface so the intake is clear. Close browser tabs a group at a time and listen for the fan dropping. Check the task manager for a process holding a core. If the vents are visibly dusty, compressed air in short bursts with the machine off clears the grille; leave internal cleaning to a repairer, since opening a laptop can void a warranty.

When to ask for official help. A loud fan plus a machine that shuts itself down without warning is a hardware symptom, and a repairer is the right call. If the device is under warranty, your rights under the Australian Consumer Law apply in addition to whatever the manufacturer offers; the ACCC explains consumer guarantees at accc.gov.au.

Where a paid product may or may not help. Security software has no bearing on cooling. The one indirect link is that some unwanted software mines cryptocurrency and keeps the processor busy, which does produce exactly this symptom; if the task manager shows an unfamiliar process holding a core at full use and you cannot identify it, a scan is worth running.

Why does it take so long to start up?

Usually because too many programs have been given permission to start with the computer. Each one adds seconds, and they add up.

Likely causes. Chat applications, cloud storage clients, game launchers, printer utilities and manufacturer support tools all tend to add themselves to the startup list quietly. A mechanical hard drive rather than a solid-state one makes a large difference too, because startup is one of the most demanding things a drive does.

What to try first, at no cost. On Windows, open Task Manager and look at the Startup tab, which shows each item and an estimate of its impact; on macOS, look at Login Items in System Settings. Disable anything you do not need in the first minute after switching on — that does not uninstall the program, and you can still open it when you want it.

When to ask for official help. If an item in the startup list is required by your workplace or by accessibility software you depend on, check before disabling it. Device manufacturers publish their own support documentation for the utilities they install, and that is the accurate source for what each one does.

Where a paid product may or may not help. Security products sometimes include a startup manager, which is a convenience rather than a capability, since the same settings are already in the operating system. If you manage several household computers from one place that may be worth paying for; for one computer it is not.

The whole computer is fine but the browser crawls. Why?

Because the browser is doing far more work than the rest of the system. A browser with many tabs and several extensions is often the heaviest program on a home computer.

Likely causes. Dozens of open tabs, each holding its page in memory. Extensions that inspect every page you load, including ones installed years ago for a single task. A browser that has not been restarted in weeks. Occasionally, software installed alongside a free download that injects advertisements or redirects searches — the one case here where the cause is genuinely unwanted software.

What to try first, at no cost. Open the extensions page and remove everything you do not actively use; this single step resolves more browser complaints than any other. Restart the browser, then check the homepage and default search engine settings and put them back if they are not what you chose. Most browsers also include a reset option that keeps bookmarks and passwords.

When to ask for official help. Each browser publishes its own documentation for resetting settings and managing extensions, and that is where to find exact steps for your version. A browser that changes its settings back after you fix them is worth treating as unwanted software rather than a fault.

Where a paid product may or may not help. Software that re-establishes itself after removal is the situation where a dedicated removal tool earns its place, and paid security products generally include one. If the problem was eleven extensions and a hundred tabs, nothing you buy will fix it.

How much free disk space do I actually need?

Enough that the operating system has room to work — as a rule of thumb, keep well clear of the last few per cent. Vendors publish their own minimum requirements, and those are the figures to follow for your version; the practical point is that a nearly full drive slows everything down and can prevent updates from installing at all.

Likely causes of a full drive. Video files and phone backups. A downloads folder that has never been emptied. A cloud drive set to keep every file available offline. Old restore points and the files kept after a major update so it can be rolled back.

What to try first, at no cost. Windows and macOS both include storage tools that show what is using space by category and remove temporary files safely. Empty the recycle bin or trash afterwards, since files there still occupy space. Move video and photo archives to an external drive, and set a cloud drive to keep files online rather than mirrored locally.

When to ask for official help. The operating system vendor's own storage documentation is the right reference for which system files are safe to remove on your version, because the answer changes between releases.

Where a paid product may or may not help. Disk space is not a security question. Treat any product advertising both scanning and dramatic space savings with ordinary scepticism, and compare what it removes against what the built-in tool already removes at no cost.

Should I install a cleaner or optimiser to speed it up?

Generally no, and particularly not one you found through an advertisement. The useful functions in this category are already in the operating system.

Likely causes of the temptation. These products advertise against exactly the symptoms on this page, and present results as large numbers of problems found, where a problem may be a leftover entry in a settings file. Some are legitimate tools with narrow uses. Others install extra software alongside themselves, change browser settings, or charge a subscription for a scan that reports issues it then asks you to pay to fix.

What to try first, at no cost. Everything in the section above: storage tools, startup items, extensions, updates. These cover the genuine functions of a cleaner. If you want to see what is running, the task manager shows it without installing anything.

When to ask for official help. If you have already paid for a tool of this kind and believe its claims were untrue, misleading or deceptive conduct by a business is covered by the Australian Consumer Law, and the ACCC explains how to make a report at accc.gov.au.

Where a paid product may or may not help. A mainstream security product from a known publisher is a different category from an optimiser, and worth keeping separate in your thinking. If you do decide to pay for security software, buying it from the vendor's own site rather than through an advertisement that appeared during a slowdown is the safer habit.

At what point is the machine simply too old?

When it no longer receives security updates, or when the work it is slow at is work you do every day. Age alone is not the measure.

Likely causes. An operating system version that has reached the end of its support period. A mechanical hard drive in a world of software written for solid-state ones. Memory that was adequate for the software of its day and is not for today's browsers.

What to try first, at no cost. Check which version of the operating system you are running and whether the vendor still supports it; Microsoft and Apple both publish their support timelines. If the hardware can take a supported version, upgrading is the single most valuable change you can make. A clean reinstall can also return several years of accumulated slowdown.

When to ask for official help. A repairer can tell you whether memory or a solid-state drive can be fitted, which on some machines is inexpensive and on others impossible because components are soldered. For disposal, councils publish local electronic waste collection points.

Where a paid product may or may not help. Security software cannot compensate for an unsupported operating system. Once updates have stopped, the gap is in the system itself, and no product closes it. If you are running an unsupported version, moving to a supported one matters considerably more than anything you could buy.