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Your PC is showing "Not enough disk space". You don't know what to delete without breaking something. You're afraid to touch the system files. In short, you're stuck.
Here's the clean method I use with my clients, with the areas where you can trim safely and the ones to leave well alone.
Why a full drive slows your PC down
Once it's more than 85-90% full, both Windows and macOS start to slow down badly:
- The system needs free space for its temporary files (the "swap" when the RAM is full).
- Windows updates fail for lack of space — which creates inconsistencies.
- On an SSD, the fuller the drive, the slower writing becomes (an internal mechanism).
Healthy target: keep at least 15-20% free space at all times. On a 256 GB SSD, that means never going above ~200 GB used.
See what's taking up space (without guessing wrong)
Before deleting things at random, you need to see who is taking up the space. Free tools I recommend:
On Windows: WizTree (free, download it from the official site diskanalyzer.com). It runs a full scan in 10 seconds and shows a clear visual of the largest folders and files. It's the tool I use on call-outs.
Built-in alternative: Settings → System → Storage. Less detailed, but it already gives a good overview.
On Mac: DaisyDisk (€10, though the free trial is often enough) or the built-in tool Apple menu → System Settings → General → Storage → Manage.
Golden rule: look first, delete afterwards. 90% of the savings always comes from 2-3 large folders you never suspected (holiday videos, obsolete iPhone backups, the Downloads folder...).
On Windows: what you can safely delete
1. Empty the Downloads folder. It's almost always the first culprit. Downloaded and forgotten installers, duplicate ZIP files, photos downloaded from emails. Clear it out once a quarter, no hesitation.
2. Empty the recycle bin. Obvious, but often forgotten. On family PCs, I regularly find 30-50 GB sitting in the recycle bin.
3. Disk Cleanup + Storage Sense. Settings → System → Storage → Clean now. Tick "Temporary files", "Windows Update cache", "Previous Windows versions". Easily recovers 5-30 GB.
4. Uninstall the programs you no longer use. Settings → Apps. Sort by size. Uninstall finished games, Adobe trials, old utilities.
5. Clear the browser cache. Chrome / Edge / Firefox build up gigabytes of cache. In the browser: Ctrl+Shift+Del → tick cache, delete.
6. iPhone backups in iTunes/Apple Devices. If you sync your iPhone to your PC, the backups often take up 50-150 GB and nobody thinks about them. Clear them in the Apple Devices app or iTunes (Preferences → Devices).
What NOT to touch on Windows: the Windows, Program Files, ProgramData, Users\Default and AppData folders (except in specific cases). Never delete files that you don't recognise on the C drive. When in doubt, leave it alone.
On Mac: the right habits
1. Downloads folder and bin — same logic as Windows.
2. Built-in storage management tool. Apple menu → Settings → General → Storage. Apple automatically flags the biggest space users: Photos, Apple TV (downloaded films), Mail, Messages (attachments).
3. Old Time Machine backups on the internal drive. If you no longer have an external Time Machine drive plugged in, the Mac keeps local backups ("snapshots") that take up space. In the terminal: tmutil listlocalsnapshots /. Or, more simply: clear and reconnect Time Machine, or turn Time Machine off temporarily.
4. Optimised Photos library. Turn on "Optimise Mac Storage" in Photos → Settings. The originals stay on iCloud, and the local versions are compressed when space is needed.
The iCloud / OneDrive / Drive storage trap
A lot of my clients get caught out without realising it: they pay for an iCloud or OneDrive subscription to keep "their files in the cloud", but in reality the files are also downloaded locally and take up space on the PC.
The fix: switch to "on-demand" mode.
- OneDrive (Windows): Right-click the blue icon → Settings → Backup tab → turn on "Files On-Demand". The files stay visible but are only downloaded when you open them.
- iCloud Drive (Mac): Settings → iCloud → tick "Optimise Mac Storage". Older files are offloaded automatically when space runs short.
- Google Drive: via Drive for Desktop, choose "Stream" instead of "Mirror". The files stay in the cloud, visible locally on demand.
A real case: a client in Cannes, a 256 GB MacBook Air permanently full. He was paying €9.99/month for 2 TB of iCloud... but had everything locally too. Turning on iCloud optimisation: 180 GB freed instantly, without losing anything.
If nothing works: move up to a bigger drive
You've done the clean-up and you're still at 95%? Your drive is simply too small for what you do. Modern usage (high-resolution photos, 4K videos, large software) no longer fits on 128 or 256 GB.
On a desktop PC or an upgradeable Windows laptop, you can replace the SSD with a bigger one. To go from 256 GB to 1 TB, budget €70-90 for the part + €80-120 for labour (including a clone of your existing system — no need to reinstall everything).
On a modern MacBook or ultraportable, the SSD is soldered: impossible to upgrade. Fallback solution: an external SSD (SanDisk Extreme 1 TB ~€100) to offload the large files (videos, photo archives).
Drive full on a PC or Mac in Le Cannet, Cannes or Mougins? I come to your home or take it into the workshop, identify what's taking up the space, clean up what is safe to remove, and if needed upgrade the drive (clone included — you get your machine back identical but bigger). Diagnosis €0, firm quote before any work. See the optimisation service or get in touch.