Why your computer is slow — 7 fixes that actually work

A slow computer almost never means a broken computer. In our experience the cause is one of seven things — and six of them cost nothing to fix. Work down this list in order.

1. Too many programs starting with the computer

Every program that launches at startup steals memory for the whole session. This is the single most common cause of a machine that was fine last year and crawls today.

Windows: press Ctrl + Shift + Esc, open the Startup apps tab, and disable anything you do not need the moment you log in. Chat apps, update helpers and printer utilities are safe to disable — they still work when you open them.

Mac: System Settings → General → Login Items, and remove what you do not need.

2. The disk is nearly full

Both Windows and macOS need free space to work in. Once you drop below roughly 10% free, everything slows down. Check your drive — if it is in the red, that is your answer.

Clear downloads, empty the recycle bin or trash properly, and move photos and videos to an external drive or cloud storage. Freeing 20–30 GB often transforms the machine.

3. A browser carrying too much weight

If the computer is only slow when you are online, the browser is the problem, not the computer. Twenty open tabs and a handful of extensions will use more memory than everything else combined.

Remove extensions you did not deliberately install, and keep tab counts sane. If your browser homepage or search engine changed without you asking, treat that as a sign of unwanted software and read point 5.

4. Updates that never finished

A half-applied update can leave a machine grinding in the background for days. Run Windows Update or macOS Software Update, let it finish completely, and restart properly — not just close the lid.

5. Malware or “optimiser” software

Anything promising to clean, boost or speed up your PC for a fee is very often the thing slowing it down. Genuine malware is quieter: unexpected pop-ups, a changed browser homepage, or fans running constantly while you do nothing.

Run a full scan with the security software already built into your system (Windows Security is genuinely good), and uninstall any “PC cleaner” you did not deliberately buy.

6. Not enough memory for what you actually do

If you routinely keep many tabs, a video call and a spreadsheet open at once, 4 GB of RAM will never feel fast. This is the one fix that costs money — but on many desktops and some laptops a memory upgrade is inexpensive and buys years.

7. An old mechanical hard drive

If your machine predates about 2017 and still has a spinning hard drive, replacing it with an SSD is the single biggest speed improvement available. It is a bigger change than a new processor, and far cheaper than a new computer.

How to tell which one it is

Open Task Manager on Windows or Activity Monitor on a Mac and look at what sits near the top while the machine is slow. If memory is pinned near 100%, look at points 1, 3 and 6. If the disk stays at 100%, look at points 2, 4 and 7. If the processor is busy while you are doing nothing at all, look at point 5.