There are two types of cleaning a PC needs regularly, and they have nothing in common. The first is physical: dust, clogged fans, dried-out thermal paste. The second is software: junk files, startup programs, bloatware. Both contribute to slowdowns, but not in the same way, and not with the same solutions.
This guide covers both in detail, with what really works and what's best avoided.
Part 1 : Physical cleaning: the dust that kills PCs
Why dust is a serious problem
A PC generates heat. The components, processor, graphics card, power supply, need to be cooled constantly. Fans draw cold air in from outside and expel the hot air. The dust, carried by that air, builds up on the grilles, the filters and especially on the processor's heatsink.
The result: air no longer flows properly. Temperatures rise. The processor then automatically triggers what's known as thermal throttling : it reduces its operating frequency to avoid damage. Your PC becomes slow even though nothing has changed in software.
Over time, high temperatures wear out the motherboard's capacitors, degrade the solder of components, and shorten the lifespan of drives and fans. A PC poorly maintained thermally ages two to three times faster than a clean PC.
In practice, I regularly open laptops at the workshop with heatsinks so clogged that no air passes through at all. The owner thinks their PC is "too old", in reality, a clean + new thermal paste gives it 5 more years of life.
Symptoms that indicate a clean is needed
- The fan(s) run loud and often, even for light tasks
- The area above the keyboard (laptop) is hot to the touch after 15–20 minutes of use
- Performance drops progressively over a session, fast at start, slow after an hour
- Windows 10/11 shows high temperatures in Task Manager → Performance tab → CPU
- Heat exhaust is noticeable through the air vents
Download HWMonitor (free, hwinfo.com) and let it run while you use your PC normally for 30 minutes. If the processor regularly exceeds 90°C, there's a thermal problem to address. Between 70 and 90°C under heavy load, it's within limits but worth watching. Below 70°C under load, all is well.
What you need
- A can of compressed air (~€8–12 at a supermarket or on Amazon). It's the basic tool, irreplaceable.
- Thermal paste (~€8–15 for a tube of Noctua NT-H1 or Arctic MX-4, the two market references). Enough for 5–10 applications.
- Isopropyl alcohol 90%+ (~€5) and cotton buds to clean off the old paste.
- A Phillips screwdriver suited to your model (often Phillips #0 or #1 for laptops).
- An anti-static surface or simply a wooden table, away from carpets.
Never use your home vacuum to clean the inside of a PC. A vacuum generates static electricity that can damage electronic components. It also pulls on fragile cables. And it just moves the dust around without removing it effectively. The can of compressed air is the only solution.
Complete physical cleaning procedure
- 1Shut down the PC completely and unplug all cables, power, monitor, keyboard, USB. For a laptop, remove the battery if it's removable. Wait 2 minutes for the capacitors to discharge.
- 2Open the case (desktop: screws on the back, left side panel) or the rear cover (laptop: Phillips screws under the device, sometimes hidden under stickers or rubber feet).
- 3Outdoors or in a well-ventilated room, blow compressed air in short bursts on the air vents, fans, processor heatsink and graphics card. Hold the fans still with a finger or a pencil before blowing, letting them spin freely under compressed air can damage the bearings.
- 4Clean the heatsink carefully: that's where dust accumulates most densely, sometimes forming a real plug between the fins. Blow perpendicular to the fins to push the dust out the other side.
- 5Remove the heatsink, clean the old thermal paste off the processor and the heatsink face with a cotton bud soaked in 90%+ isopropyl alcohol. Apply a new amount of paste the size of a rice grain to the centre of the processor. Refit the heatsink, tightening the screws in the right order (often in a cross pattern or numbered).
- 6Close the case or the cover, reconnect all cables, boot the PC and check the temperatures with HWMonitor after 15–20 minutes of normal use. A drop of 15 to 25°C under load is typical after this operation.
Dusting a desktop PC : steps
- Shut down the PC and unplug all cables, including the power.
- Open the case (screws on the back, left side panel in general).
- Outdoors or in a well-ventilated room (dust will go everywhere), blow compressed air in short bursts on the grilles, fans, processor heatsink and graphics card.
- Hold the fans still with a finger or a pencil before blowing on them, making them spin at high speed with compressed air can damage the bearings.
- Clean the dust filters (some cases have them on the front and bottom faces), under water if washable, blown if not.
- Close the case.
Replacing the thermal paste : the real job
Dusting alone isn't enough if the thermal paste between the processor and its heatsink is dry. This conductive paste fills the micro-irregularities of the metal surfaces to maximise heat transfer. Over time (3 to 7 years), it dries out, cracks and loses effectiveness.
On a laptop, this is the operation that makes the biggest difference, and it's the one most people never do.
Steps:
- Remove the heatsink by undoing the screws in the indicated order (often numbered on the heatsink itself, follow the order to avoid asymmetrical stress on the processor).
- Remove the old paste with a cotton bud soaked in isopropyl alcohol, on the processor AND on the heatsink face. Be patient: the old paste is often hard.
- Apply a small amount of new paste : about the size of a rice grain in the centre of the processor. No need to spread it yourself: the heatsink pressure does the work.
- Refit the heatsink in the correct screw order, without forcing.
- Switch on and check the temperatures with HWMonitor.
The result is often spectacular: a drop of 15 to 25°C under load, quieter-running fans, and restored performance.
Cost by approach chosen
Recommended frequency
| Type of PC | Dusting | Thermal paste |
|---|---|---|
| Desktop tower | Every 2 years | Every 4–5 years |
| Laptop, everyday use | Every 2–3 years | Every 4–5 years |
| Laptop, gaming or intensive | Every 1–2 years | Every 3–4 years |
| PC in dusty environment (workshop, pets) | Every 6–12 months | Every 3 years |
If you're not comfortable opening your laptop, some models are really difficult to disassemble without experience (fragile plastic clips, short ribbon cables, screws hidden under stickers), this job is well worth the cost of a technician. At the workshop, I do it for €45, thermal paste included, with before/after temperature measurement.
Part 2 : Software cleaning: what's actually worth doing
The base rule: less is often more
"Software cleaning" is a sector overrun with useless, sometimes harmful programs that pretend to improve Windows when they often just slow it down further or create new instabilities. I'll be direct: most "software cleaning" actions have negligible impact on performance.
What really has an impact is simple, free, and built into Windows.
What really works
Empty the Recycle Bin and the Downloads folder Mundane but real: a drive that fills up ends up slowing down (especially SSDs above 80% full). Regularly empty the Recycle Bin and the Downloads folder, the latter is often a graveyard of forgotten installer files.
Uninstall unused programs Not for space reasons, but because some programs run in the background at startup. Settings → Apps → Apps & features. Uninstall anything you haven't opened in 6 months.
Clean up startup programs This is the most impactful action. Open Task Manager (Ctrl + Shift + Esc) → "Startup" tab. Disable everything that isn't essential: Spotify, Discord, OneDrive (if you don't use it), Teams, driver software that doesn't need to run permanently. Each program disabled here = faster startup and less RAM used at idle.
Clean the disk with Windows' built-in tool Type "Disk Cleanup" in the Start menu. Run it and tick all the boxes. On a PC that hasn't been cleaned for a long time, this can free up 5 to 15 GB. Also click "Clean up system files" to delete old Windows installations (the Windows.old folder after an upgrade).
Update Windows and the drivers Updates often bring performance optimisations, not just security fixes. Graphics card drivers in particular have a direct impact on game and video rendering performance.
What not to do
CCleaner: once useful, this tool was compromised in 2017 (a distributed version contained malware). Since then, Avast (which bought CCleaner) has turned it into aggressive nagware. Its main function, cleaning the Windows registry, is at best useless, at worst dangerous. Don't touch the Windows registry unless you're an experienced technician. Registry cleaning doesn't make Windows perceptibly faster and can break software.
Advanced SystemCare, Ashampoo WinOptimizer, PC Speed Maximizer and similar: these programs feed off the myth that Windows needs to be "optimised" in depth. They do little or nothing useful, display alarmist warnings to push you to buy the premium version, and often slow the PC down more than they improve it (since they run in the background permanently).
Defragmenting an SSD: never do this. Defragmentation is useful on mechanical hard drives, it's useless and potentially harmful on SSDs (it wears down the memory cells with no benefit).
If an ad, a website or an email tells you that your PC has X critical errors and offers software to fix them, it's always a scam or malware. Windows never diagnoses your PC via a web page. Close the tab.
The real software solution: a clean reinstall
If your PC has accumulated years of installations, partial uninstalls, stacked updates, at some point, no surface cleaning will be enough. The radical and definitive solution is a clean reinstall of Windows: start from a fresh system, only reinstall what you need.
It's the option I recommend when the PC is more than 4–5 years into the same installation, or after a serious virus infection. It takes 2–3 hours and literally transforms the user experience, but it requires backing up your data beforehand.
What I recommend in practice
Here's my software maintenance protocol, with no paid third-party software:
- Every month: empty Recycle Bin + Downloads
- Every 3 months: run Windows Disk Cleanup, check for Windows updates
- Every 6 months: review startup programs, uninstall unused software
- Every 2–3 years: consider a clean reinstall of Windows if the system seems unstable
Combined with regular physical cleaning, this simple protocol keeps a PC healthy for years.
Your PC running hot, noisy or gradually slowing down? I clean it, replace the thermal paste and give it a full check at the workshop.
In summary
| Action | Real impact | Frequency |
|---|---|---|
| Dusting (compressed air) | High, temperatures and noise | Every 2 years |
| Thermal paste replacement | Very high, up to -25°C | Every 4–5 years |
| Cleaning up startup programs | High, startup + RAM | Every 6 months |
| Windows Disk Cleanup | Medium, free space | Every 3 months |
| CCleaner / registry cleaners | None to negative | Never do |
| Clean Windows reinstall | Very high if system is old | Every 4–5 years |
A regularly maintained PC isn't a PC you repair often, it's a PC that doesn't break down.
Frequently asked questions
How often should you clean your PC?+
Can cleaning really gain you 20°C?+
Can I clean my laptop myself?+
Which thermal paste should I choose?+
How much does PC cleaning cost in Poitiers?+
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