A computer running slow is usually caused by one of four things: too many programs starting with Windows, a full or failing hard drive, not enough memory (RAM) for the way you use it, or malware. In most cases you can identify which one it is in under 20 minutes using the checks below, and several of the fixes cost nothing.
This guide walks through nine fixes in the order a technician would try them, from the free and safe to the ones that involve opening the case. At the end we explain the point where it is genuinely cheaper to hand the machine to a professional than to keep experimenting.
Key takeaways
- Startup programs and browser tabs are the most common reason for a computer running slow, and both are free to fix.
- If the drive is over 90% full, or the machine still uses a spinning hard disk, storage is almost certainly the bottleneck.
- Running out of RAM shows up as freezing when you switch between programs, not as a slow boot.
- Persistent slowness plus pop-ups, a spinning fan at idle or unknown programs points to malware.
- A laptop or desktop that is five years old or younger is nearly always worth an SSD or RAM upgrade rather than replacement.
Why is my computer running slow? Find the cause first
Before changing anything, spend two minutes in Task Manager (press Ctrl + Shift + Esc on Windows, or open Activity Monitor on a Mac). Look at the CPU, Memory and Disk columns:
| What you see | Likely cause | Jump to fix |
|---|---|---|
| Disk at 100% for minutes after boot | Old hard disk, Windows updates or indexing | Fixes 1, 5, 6 |
| Memory over 85% with normal programs open | Not enough RAM, or a memory-hungry browser | Fixes 3, 7 |
| CPU at 100% with nothing open | Malware, a stuck update or a failing fan | Fixes 4, 8 |
| Everything low but still sluggish | Storage almost full, heavy startup list or overheating | Fixes 1, 2, 8 |
If the drive is the problem, the numbers make it obvious. A computer running slow with disk usage pinned at 100% while CPU and memory sit at 10% is not going to be cured by deleting files – it needs faster storage.
9 proven fixes for a computer running slow
1. Trim the startup list
Every program set to launch at login competes for the drive and CPU for the first few minutes. Open Task Manager, click the Startup apps tab, and disable anything you do not need immediately: chat apps, printer utilities, game launchers, cloud sync tools you can open later. Leave security software enabled.
On a Mac go to System Settings → General → Login Items. Restart afterwards and time how long it takes to reach a usable desktop. On many machines this single step halves boot time.
2. Free up storage space
Windows and macOS both need free space to create temporary files and manage memory. Once a drive passes 90% full, a computer running slow becomes almost guaranteed. Run Storage Sense (Windows) or Manage Storage (Mac), empty the Recycle Bin, clear the Downloads folder and uninstall programs you have not opened this year.
Aim for at least 15–20% free. If you cannot get there because of photos and videos, move them to an external drive or cloud storage rather than deleting them.
3. Tame your browser
Modern browsers are memory monsters. Thirty open tabs in Chrome can consume 4–6 GB of RAM on their own, which on an 8 GB machine leaves almost nothing for everything else. Close tabs you are not using, remove extensions you do not recognise, and consider a tab-suspending extension if you habitually keep dozens open.
Also check the extension list carefully. Malicious extensions are one of the more common infections we see in Melbourne homes, and they slow the browser dramatically while stealing data.
4. Run a full malware scan
Malware does not always announce itself. Cryptominers, adware and spyware run quietly in the background, using CPU and network bandwidth, and the only symptom is a computer running slow for no apparent reason. Run a full (not quick) scan with Windows Security or your installed antivirus, then follow up with a second-opinion scanner such as Malwarebytes Free.
If the scan finds something it cannot remove, or the slowness returns within days, stop there. Deep infections are worth professional attention – our virus and spyware removal service cleans the system without wiping your files where possible. The Australian Cyber Security Centre also publishes plain-English guidance on recognising and removing malware that is worth bookmarking.
5. Install pending updates, then let the machine settle
A computer running slow immediately after a big Windows or macOS update is normal. The system indexes files, rebuilds caches and installs drivers in the background for an hour or two. Install all pending updates from Settings → Windows Update or System Settings → General → Software Update, leave the machine plugged in and idle for a couple of hours, then reassess.
Microsoft’s own support documentation has a dedicated troubleshooter for slow performance after updates, and Apple’s support site covers the Mac equivalent.
6. Check drive health
A drive that is beginning to fail slows down long before it stops working. Files take ages to open, the system freezes for a few seconds at a time, and you may hear clicking from a spinning hard disk. On Windows, open Command Prompt and run wmic diskdrive get status – anything other than “OK” is a warning. Free tools such as CrystalDiskInfo show the drive’s SMART data in more detail.
Back up immediately if you see warnings. A failing drive is a data emergency first and a speed problem second, and our hard drive repair and data recovery page explains the options if the drive is already struggling.
7. Upgrade to an SSD or add RAM
This is the fix that turns a five-year-old machine into a fast one. If your computer still runs on a mechanical hard disk, swapping it for a solid-state drive is the single most effective upgrade available – boot times drop from minutes to seconds and every program opens faster.
If the machine already has an SSD but freezes when you switch between programs, the fix is more RAM. Most home and office machines are comfortable with 16 GB in 2026; 8 GB is now the minimum for a Windows 11 PC used with a modern browser.
The catch is compatibility. Many recent laptops solder RAM to the board and some use non-standard SSD sizes, so not every machine can be upgraded. Our hardware upgrade service checks what your specific model supports before quoting, and we clone your existing drive so nothing is lost.
8. Clean out dust and check for overheating
When a processor gets too hot it deliberately slows itself down to survive – a process called thermal throttling. The symptoms are a loud fan, a hot underside on a laptop, and a computer running slow specifically during video calls, games or long work sessions. Desktops accumulate dust in the case and heatsink; laptops choke on fluff in the fan intake.
Blowing compressed air through the vents helps, but on a laptop older than three or four years the thermal paste between the processor and heatsink has often dried out and needs replacing. That is a workshop job, not a DIY one, and it is included in our standard laptop repair service.
9. Reset Windows or macOS (last resort)
If nothing above helps and the hardware checks out, years of accumulated software, drivers and registry changes may be the cause. A Reset this PC with “Keep my files” (Windows) or a clean macOS reinstall gives you a fresh system while preserving documents.
Back up first anyway. Resets occasionally fail partway, and any program you installed will need reinstalling with its licence key. If the idea of doing this yourself is stressful, remote desktop support lets a technician handle it while you watch.
When to stop DIY and call a technician
You have done the sensible things when you have trimmed startup, freed space, scanned for malware and installed updates. If the computer is still running slow after that, the cause is almost certainly hardware – a failing drive, insufficient RAM, or overheating – and the next steps involve opening the machine, cloning drives and buying parts.
Rough guide for Melbourne in 2026:
| Situation | Sensible next step |
|---|---|
| Machine under 5 years old, mechanical hard disk | SSD upgrade – usually the best value repair you can buy |
| Machine under 5 years old, 8 GB RAM, freezing | RAM upgrade if the model allows it |
| Drive health warnings or clicking | Stop using it, back up, professional data recovery |
| Machine 7+ years old, slow at everything | Compare repair against replacement – see our repair-or-replace laptop guide |
| Slowness returns after every clean-up | Persistent malware or a failing component – professional diagnosis |
Melbourne PC Repair Pro offers a free 10-minute phone consultation. Describe the symptoms and your suburb, and we will tell you honestly whether the fix is a quick remote session, an upgrade, or not worth doing on that machine. Paid work only starts after you approve a written quote.
Frequently asked questions
Why is my computer running slow all of a sudden?
A sudden slowdown usually follows a Windows update, a new program installing itself into startup, a drive filling up, or a malware infection. Check Task Manager for what is using the disk or CPU, then work through the first five fixes above.
Will more RAM fix a computer running slow?
Only if RAM is the bottleneck. Open Task Manager and look at the Memory column under normal use – if it sits above 85%, more RAM will help. If memory is fine but disk usage is at 100%, an SSD is the right upgrade instead.
Is it worth upgrading a slow computer or should I buy a new one?
If the machine is under five years old and the upgrade costs less than about half the price of a comparable replacement, upgrading is usually the better decision. Older than seven years, or slow at basic tasks even after an SSD, and replacement starts to make more sense.
Can a virus make my computer run slow?
Yes. Cryptominers, adware and spyware consume CPU, memory and bandwidth in the background. A full antivirus scan plus a second-opinion scanner will find most infections; anything that keeps coming back needs professional removal.
How long should a computer take to start up?
A machine with an SSD should reach a usable desktop in 15–30 seconds. A mechanical hard disk typically takes 1–3 minutes. Anything longer than that, on either type of drive, indicates a problem worth investigating.
