Given your goal (“maximum certainty” for a
space/mystery files situation) and the fact you only have the standard
EFI/System + Windows + Recovery partitions, the most reliable method is:
Recommendation for maximum certainty
USB clean install + delete all partitions on the OS disk
This is the closest you can get to a “known clean baseline” on that drive, because you are not relying on the existing Windows install, existing partition layout, or any recovery image.
A Windows “Reset this PC” can work, but it’s less deterministic: it usually keeps the existing partition structure and recovery environment, and it’s fundamentally a rebuild performed
from within your current setup (even if it downloads Windows from the cloud).
This aligns with the general troubleshooting approach we discussed earlier: when diagnostics/cleanup don’t explain tens of GB and you want a guaranteed fresh state, a true clean install becomes the reasonable last step.
What carries over (or not)
A) Viruses / “junk” / broken links / orphaned files
USB clean install (delete partitions):
- Does not carry over old
Windows, Program Files, Users, Windows Update cache, broken shortcuts, orphaned folders, etc. (because those partitions are removed).
- Windows.old: typically not created in this scenario, because you aren’t doing an upgrade/keep-old install.
Reset this PC → Cloud download → Remove everything:
- Usually removes apps and user data, but it’s not as “surgical” as deleting partitions.
- If you choose the option to clean the drive, it’s more thorough (slower), but it still typically keeps the recovery setup/partitions rather than rebuilding the disk layout from scratch.
Important caveat for both methods: neither one “magically” cleans:
- malware in UEFI/firmware (rare, but possible),
- other drives (you said you don’t have other partitions/drives, so that’s simpler),
- data that will sync back from a Microsoft account (OneDrive, some settings, browser data, etc..
B) The “mystery 60 GB” scenario specifically
In cases like yours, the missing space is often something like VSS/shadow storage, update caches, hiberfil/pagefile, WSL/VM disks, etc.
A clean install doesn’t “fix” the underlying Windows storage mechanisms—but it
does remove whatever hidden consumer existed
on that installation, because the old installation is gone.
Disk space used after updating (clean install vs reset)
In general,
after you fully update to the current patch level, the Windows footprint ends up
similar in both cases, because:
- the same cumulative updates land,
- WinSxS/component store grows similarly,
- pagefile/hiberfil behavior is similar (unless you change settings).
Where you may see a difference:
- OEM preload / OEM utilities: Reset can sometimes bring back OEM apps/tools depending on how the vendor configured recovery; USB clean install tends to be “leaner” because you only install what you want.
- Recovery partition: you’ll still have a recovery partition either way, but a clean install gives you the most control over what exists on the disk.
So:
don’t expect a dramatic permanent “GB difference” purely from the method—expect the difference to come from
what gets reinstalled and what gets synced back.
Performance (speed)
If both end states have:
- the same Windows 11 25H2 build,
- the same drivers,
- the same startup apps,
- the same background utilities,
…then performance is typically
the same.
Where clean install often “feels faster” in the real world:
- fewer OEM background apps,
- fewer startup entries,
- less accumulated config cruft.
The “best-practice” clean-install procedure for your setup (3 partitions only)
Since you only have the standard partitions, this is straightforward:
1)
Back up your personal files (and export anything you care about: browser bookmarks, password manager vault, license keys if needed).
2)
Create a Windows 11 USB installer (Microsoft Media Creation Tool / official ISO).
3) Boot from USB → when you reach
“Where do you want to install Windows?”:
- Select each partition on Disk 0 (EFI/System, Primary, Recovery) and click Delete until you see Unallocated space.
- Select the unallocated space → Next. (Windows will recreate the needed partitions automatically.
4) After install:
- Install chipset/network drivers if needed (often Windows Update handles most).
- Run Windows Update fully.
- Reinstall apps manually (avoid “driver booster” / “registry cleaner” type tools).
5) If you want to avoid old junk reappearing via sync:
- temporarily pause OneDrive and/or be selective about what you sync back,
- consider setting up first with a local account, then sign in after (optional).
Optional “nuclear” wipe: using DiskPart
clean all will write zeros to the entire drive (very slow and unnecessary for most users, and it adds SSD wear). For your goal (clean OS + remove mystery files), deleting partitions in Setup is usually enough.
When Reset (cloud) is still a reasonable choice
If your main goal is “fresh Windows fast” and you don’t care about partition-level certainty, then
Reset → Cloud download → Remove everything + Clean the drive is the most thorough reset option.
But since you explicitly want
maximum certainty for a space mystery, I’d pick the USB clean install.
If you want, I can tailor the steps to your exact machine:
1) Is your mini PC using
BitLocker/device encryption right now? (If yes, you’ll want to save the recovery key before reinstall.
2) Do you want to keep
OEM recovery tools, or you don’t care if they’re gone?