"Cleaning" covers two separate complaints: a drive that is full, and a computer that feels slow. They need different fixes, so start by deciding which one you have.
If the drive is full
- Run Disk Cleanup as administrator and include system files,
- Remove the previous Windows installation once the update has proven stable,
- Sort your apps by size and uninstall what you no longer open,
- Move photos, video and archives to an external drive or cloud storage,
- Clear application and browser caches with a tool such as BleachBit.
If the PC feels slow
- Task Manager, Startup tab — disable everything that does not need to launch at boot,
- Check for a background process pinning the CPU or disk at 100%,
- Confirm you are on an SSD; a mechanical boot drive is the single biggest cause of sluggish modern Windows,
- Check installed RAM against what you actually run — 8 GB is tight with a browser and Teams open,
- Install pending Windows and driver updates, then restart properly rather than closing the lid.
A monthly routine that takes ten minutes
- Empty the Recycle Bin and Downloads,
- Run your cleanup tool on browser and temporary file categories,
- Glance at startup entries for anything new that added itself,
- Check free space on C: and act before it turns red.
Things that do not help
Registry cleaners, "RAM boosters", and any tool that promises a percentage speed increase. Defragmenting an SSD is unnecessary and Windows handles it correctly on its own. Skepticism saves more time here than any utility.
Related reading: what is safe to remove and choosing a cleanup tool.