Guide · 5 min read
Why is my computer slow? Causes and fixes
A slow computer usually has a clear cause - an old hard drive, too little memory, startup clutter or malware. Here is how to find which one it is and fix it.
A computer that takes forever to start, stalls when you open a spreadsheet or spins its fans for no obvious reason wastes time all day long. It is tempting to assume the machine is simply old and needs replacing, but slowness usually has a specific cause, and many of those causes are inexpensive or free to fix. Finding the real one is the first and most important step.
This guide covers the common reasons Windows and Mac computers slow down, how to spot each one using the tools already on your machine, and what you can safely do about them yourself. If you work through it and the computer is still dragging, you will at least know what to tell a technician, which makes the fix quicker.
From $135 + GST + $30 call-out ($185.25 incl. GST)
Quick checklist
- Restart properly rather than just closing the lid
- Open Task Manager or Activity Monitor and note what is busiest
- Trim the startup list
- Uninstall programs you no longer use
- Run a full security scan
- Free up space on the main drive
- Check the vents are clear and the fan is not roaring
- Install pending Windows or macOS updates
See what is keeping the computer busy
On Windows, press Ctrl, Shift and Esc together to open Task Manager, then look at the Processes tab. Sort by CPU, Memory and Disk in turn to see which programs are working hardest. On a Mac, open Activity Monitor from the Utilities folder. If one program sits near the top constantly, that is your lead. If Disk use is pinned high while nothing much is happening, the storage drive itself is often the bottleneck.
An old spinning hard drive
Many computers still in use, especially budget models from some years back, run on a mechanical hard drive. These are far slower than a modern solid state drive, and they slow down further as they age and fill up. Signs include a long startup, a constantly busy disk light and Task Manager showing the disk at full use. Replacing it with an SSD and moving everything across is usually the most noticeable improvement an older computer can get.
Not enough memory
Memory, or RAM, is where the computer keeps the programs you are using right now. When it runs short, the computer shuffles data to and from the storage drive, which slows everything down. Web browsers with lots of tabs, Microsoft Teams and accounting software all use plenty. If Task Manager shows memory consistently near full during normal work, adding more RAM, where the laptop or desktop allows it, can make multitasking feel smooth again.
Too much running at startup
Over time, programs quietly add themselves to the startup list - printer utilities, update checkers, cloud sync tools and trial software that came with the computer. Each one takes a slice of memory and processor time before you have opened anything. Trimming the list is free, safe when done carefully, and often makes a slow, sluggish startup noticeably quicker. Restart afterwards to see the difference.
- Windows: Task Manager, then the Startup tab
- Mac: System Settings, General, Login Items
- Disable anything you do not need at sign-in
- Uninstall trial software and toolbars you never use
- Leave security software and drivers enabled
Malware and unwanted programs
Malicious software and adware often show up as slowness before anything else. Watch for browser home pages you did not choose, new toolbars, pop-ups that appear when no browser is open, or unknown programs high in Task Manager. Run a full scan with your security software and check the installed programs list for anything you do not recognise. If you suspect a stranger has had remote access to your computer, disconnect it from the internet and get help rather than cleaning it up yourself.
Heat, dust and a full drive
Laptops and desktops deliberately slow themselves down when they get too hot, to protect the processor. Blocked vents, dust built up inside and using a laptop on a bed or couch all trap heat. A drive that is almost full also hurts performance, because the system needs free space for updates and temporary files. Clear out old downloads, empty the recycle bin and move old photos to an external drive or cloud storage. Keep a healthy amount of space free on the main drive, and make sure the vents have room to breathe.
When to call a technician
Book a computer health check if the machine is still slow after these steps, if you suspect a failing drive, or if malware keeps coming back. We test the drive's health, check memory use and temperatures, remove unwanted software, tidy startup and updates, and tell you plainly whether an SSD or RAM upgrade will help. If the computer is not worth upgrading, we say so before any work is done.
From $135 + GST + $30 call-out ($185.25 incl. GST)
Related services
Computer Health Check & Tune-upA full check of a computer's drive, updates, security, startup items, backups and cooling, with a written list of findings.Computer UpgradesSSDs, memory, Windows 11, graphics cards and power supplies fitted - with honest upgrade-or-replace advice.Virus & Scam RemovalPop-ups, scam calls and nasty software cleaned up.Common questions
Will a factory reset make my computer fast again?
It can help if software clutter is the cause, but it wipes your programs and settings, and it does nothing for an old hard drive or too little memory. Back up first, and try the simpler fixes in this guide before reaching for a full reset.
Does adding an SSD really make that much difference?
On a computer with a mechanical hard drive, yes. Startup, opening programs and searching files all become far quicker. If the computer already has an SSD, the gain from replacing it is small, and memory or the processor is more likely to be the limit.
Is my computer slow because of a virus?
It can be, but most slow computers are not infected. Old drives, low memory and startup clutter are far more common causes. Run a full scan to rule malware out, and look for warning signs such as pop-ups, changed home pages or programs you did not install.
Should I use a cleaner or booster program?
We generally advise against them. Many speed-up tools do little that Windows or macOS cannot do itself, and some come bundled with adware or push paid upgrades with alarming warnings. The built-in tools covered in this guide are safer and cost nothing.
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