Slow laptop: the real causes and what actually works

"My PC is slow", it's probably the sentence I hear most often at the workshop. And yet, behind that simple complaint hide very different causes. Cleaning up temporary files or uninstalling software is often just a surface fix.

This guide helps you identify the real cause of the slowdown, and pick the right solution.

The most common culprits#

1. A mechanical hard drive (HDD)#

By far the number one cause. If your PC is more than five years old and has never been upgraded, it almost certainly has a mechanical hard drive : the little clicking sounds you sometimes hear at startup, that's it.

These drives work with platters spinning at 5,400 or 7,200 rpm and a mechanical read head. Slow by design, they get even slower as they age.

Fix: replace it with an SSD. This is the upgrade that changes performance most radically. A PC that booted in 3 minutes will boot in 15–20 seconds afterwards. Labour is €20 at the workshop (data migration included), plus the price of the SSD. See detailed pricing.

2. Not enough RAM#

RAM is your PC's working memory, the place that holds open programs. If you have 4 GB of RAM and you open Chrome with several tabs + Word + Teams, your PC is going to drag.

Windows 10 and 11 alone use around 2 GB at idle. That leaves very little for your applications.

Practical thresholds:

• 4 GB: insufficient today for everyday use
• 8 GB: minimum comfortable for office work + web
• 16 GB: recommended if you keep several applications open at once
• 32 GB+: for video editing, gaming, virtualisation

Fix: add RAM. Depending on the PC, that's possible for €20–€60 (the cost of the stick) plus labour. Watch out: some laptops have RAM soldered to the motherboard, not upgradable.

3. Overheating and thermal throttling#

A PC that runs too hot automatically reduces its processor performance to avoid damage. This mechanism is called thermal throttling.

Characteristic symptoms:

• The PC is normal at startup, then gradually slows down after 15–20 minutes of use
• The fan runs constantly at full speed
• The keyboard area is very hot to the touch

Cause: the thermal paste between the processor and the heatsink has dried out. It dries naturally after 3–5 years. The fan can also get clogged with dust.

Fix: clean + replace thermal paste. Immediate result: the PC regains its full power. Cost: €45 at the workshop.

4. Malware or bloatware#

A virus, a spyware program or a cryptocurrency miner can grab 40–80% of the processor in the background. Your PC drags even when you're doing nothing.

Bloatware (useless preinstalled software that launches at startup) has the same effect, without being malicious.

How to check quickly: open Task Manager (Ctrl + Shift + Esc), Processes tab. If something is using 50%+ of the CPU for no obvious reason, that's suspicious.

Fix: a good antivirus + full scan + cleanup of startup software. In severe cases (persistent virus, rootkit), a clean reinstall of Windows is more effective than any cleanup.

5. Ageing Windows and fragmentation#

Windows accumulates temporary files, orphaned registry entries and partial updates over time. On an SSD, fragmentation isn't an issue, on a hard drive, it slows down access.

It's rarely the main cause, but it contributes. A clean reinstall of Windows fixes this for good, as long as the hardware problems are sorted first.

6. Failing battery#

A battery in poor condition can force the PC to reduce its performance to preserve remaining runtime, even when plugged into the mains in some cases (Windows power management).

Check the state of your battery: type powercfg /batteryreport in a terminal and review the generated report.

How to diagnose it yourself#

1. 1
   Check the type of drive, type 'Defragment and Optimise Drives' into the Windows search bar. If it shows 'Hard disk drive' (HDD) rather than 'Solid state drive', you have a mechanical drive: that's very likely the main cause of the slowdown.
2. 2
   Check the RAM, open Task Manager (Ctrl + Shift + Esc), Performance tab, then Memory. If usage exceeds 80–90% when you have almost nothing open, your RAM is insufficient for your usage.
3. 3
   Check the temperature, download HWMonitor (free, hwinfo.com). Run your PC normally for 15 minutes and look at the processor temperatures. If they exceed 90°C in standard use, there's a cooling problem, dried thermal paste or a clogged fan.
4. 4
   Check startup programs, Task Manager → Startup tab. Every program listed launches automatically when Windows starts. Disable (right-click → Disable) anything non-essential: Teams, Spotify, OneDrive, manufacturer utilities… That alone can cut your boot time in half.

Budget to get a PC back in shape#

Here are the real ranges I charge at the workshop in 2025 (labour included):

What not to do#

• ❌ Disabling the antivirus to "gain speed", a very bad idea
• ❌ Installing "PC cleaners" like CCleaner or Advanced SystemCare, at best useless, at worst dangerous
• ❌ Reformatting without diagnosing : if the problem is hardware (drive, RAM), reformatting won't change anything

When to consider a new PC?#

Repair or upgrade is generally worth it if:

• The PC is less than 8–10 years old
• The processor is still acceptable (Intel Core i5/i7 6th generation or newer, AMD Ryzen)
• Usage is everyday (office work, web, streaming)

Beyond that, if the processor is truly obsolete or the motherboard is failing, investing in a new PC is often more cost-effective.

I always run this calculation with the customer before any work, there's no way I'm letting you spend €150 on repairs for a PC worth €80.

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In summary#

The good news: in most cases, a slow laptop can get back to satisfactory performance with one or two targeted fixes, far less than a replacement. See detailed pricing.