Why Is My Computer So Slow?
How to Speed It Up on Windows and Mac
Is your Windows PC or Mac running slower than it used to? A slow computer is a symptom, not a diagnosis — the right solution depends on what is causing the problem.
Common causes of a slow computer include insufficient RAM, an ageing or failing hard drive, a slow storage device, too many startup or background programs, Windows or macOS issues, malware, and outdated hardware. Sometimes, a simple software fix can restore performance, while in other cases, a hardware upgrade such as replacing an HDD with an SSD can make a dramatic difference.
Before spending money on a new computer, it is worth finding out what is actually causing the slowdown. A proper computer performance check can help identify whether the problem is related to hardware, software, storage, memory, or system configuration.
In this guide, we explain the most common reasons why Windows PCs and Macs become slow, how to identify the cause, and what you can do to improve performance.
If your computer is still slow after trying the usual fixes, professional computer repair and troubleshooting may be the most practical solution. At Sunny Computer, we help customers throughout Melbourne with computer and laptop repairs, performance issues, hardware upgrades, Windows and macOS troubleshooting, and data recovery.
What Causes a Computer to Slow Down?
Age is rarely the real reason. A computer that was fast three years ago still has the same processor today. In many cases, slow performance is caused by one of these common issues:
- Nearly full drive — Keeping sufficient free space on your Windows or MacOS drive is important for smooth performance.(we suggest at least 30GB if possible)
- Insufficient RAM — When memory is full, the computer relies on much slower storage, reducing performance.
- Too many startup programs — Unnecessary apps running in the background can slow down your computer.
- Old mechanical HDD — Traditional hard drives can become noticeably slower over time and may significantly affect overall performance.
- Too many connected drives — Unnecessary or ageing hard drives can slow down startup and general computer performance.
- Heat and dust — Excessive heat can cause the computer to reduce its performance to protect the hardware.
Find the culprit — the difference on Windows and Mac
On Windows
Including Windows7, Windows10, Windows11 and so on, whether running on a Desktop PC, Laptop, All-in-one Computer or Tablet.
- Task Manager — press Ctrl-Shift-Esc to open Task Manager, and choose Performance to view CPU, Memory, Disk and Network usage
- Startup tab — in Task Manager, disable anything that is not necessary launching automatically
- Free space — Settings > System > Storage shows what is filling the drive and offers to clear temporary files
- SSD or HDD? — in Task Manager's Performance tab, the disk is labelled SSD or HDD — an HDD is your biggest upgrade opportunity
On a Mac
Including macOS versions such as Ventura, Sonoma, Sequoia and Tahoe, whether running on a MacBook, iMac, Mac mini, Mac Studio or other Mac computer.
- Activity Monitor — in Applications -> Utilities -> Activity Monitor, check the CPU, Memory, Disk and network tabs to find unusual usage
- Memory Pressure — the graph at the bottom of the Memory tab — if it lives in the yellow or red, you are short on RAM
- Login Items — System Settings > General > Login Items & Extensions -> Open at Login; check what launches automatically at sign-in
- Storage — System Settings > General > Storage, check what is filling the disk and if you have enough space for the system to run smoothly
The upgrade that actually works
If your computer still uses a mechanical hard drive (HDD), upgrading to an SSD can be transformative. It can make an older computer feel like new, at a fraction of the cost of replacing it. Adding more memory (RAM) can further improve performance.
Important Check: many thin laptops (such as Microsoft Surface Book) and newer MacBooks have storage and memory soldered to the motherboard, making them impossible to upgrade. It’s therefore worth checking your model before planning an upgrade.
What does not help as much as expected
A lot of “speed up your PC” advice online is either ineffective or potentially risky. Before spending money or making changes that could affect your data, it’s worth knowing what actually helps.
- “PC cleaners” and “Speed boosters”: These usually make little or no noticeable difference to performance, and some may include unnecessary or potentially unwanted software. We recommend avoiding them.
- Deleting files at random: Freeing up storage space can help, but deleting the wrong system files can cause problems. It’s safer to use Windows’ built-in storage and cleanup tools.
- Endless “optimising” apps: Many of the most useful performance improvements are free and already built into Windows. You generally don’t need a paid app running in the background to keep your computer running well.
- Driver updater programs: Most drivers do not need regular updating, and third-party driver updater tools can sometimes install incorrect or unnecessary drivers, causing new problems. It’s usually safer to get drivers directly from Windows Update or the computer manufacturer.
Common questions
Why is my computer slow even when I don’t have many programs open?
Why does my computer take so long to start?
Why does my computer become slower over time?
Do “PC Cleaner” or “Speed Booster” Apps Really Work?
Is My Computer Too Old to Be Worth Repairing?
Usually not. Slow performance caused by an ageing hard drive, limited memory or unnecessary software can often be improved at a reasonable cost. Replacement may make more sense if the drive is failing, the computer no longer receives security updates, or several major components need upgrading.
We’ll assess your computer and give you honest advice on whether it’s worth repairing or replacing.
Will an SSD Really Make an Old Computer Faster?
Yes. Replacing a traditional mechanical hard drive with an SSD can make a significant difference, improving startup times, program loading and overall responsiveness. For many older computers, it can be one of the most worthwhile upgrades.
However, some newer laptops and Macs have storage that is soldered to the motherboard and cannot be upgraded. We can check your model and let you know what upgrade options are available.