FAQ
TL;DR: A single-pass zero overwrite meets NIST SP 800-88 “clear” guidance and cuts consumer-grade recovery success to under 0.05 % [NIST, 2014]. “Factory reset is enough” [Elektroda, hultonetty, post #15660095] Reinstall Windows, then wipe free space; total time ≈2–3 h on 500 GB.
Why it matters: These steps let you sell a laptop without gifting your banking logins to the buyer.
Quick Facts
• NIST SP 800-88 Rev.1 accepts one-pass overwrite for magnetic drives as “Clear” [NIST, 2014].
• CCleaner offers 1, 3, 7 or 35-pass free-space wipe modes [Piriform Docs].
• A 500 GB HDD wipes in ~2–3 h at 150 MB/s SATA III speed [Backblaze, 2021].
• Chrome’s Login Data file averages 40 KB yet stores every saved password [Google, 2023].
• Replacing a used 2.5-inch HDD costs approx. €15–20 on the EU market [PriceSpy, 2024].
What is the safest way to erase personal files before selling a laptop?
Reinstall Windows or run the factory-reset image, then overwrite the remaining free space with a one-pass zero fill. This removes registry debris and unallocated clusters that could contain your passwords [Elektroda, dt1, post #15660100] A single pass meets current NIST “Clear” guidance for HDDs [NIST, 2014].
Is a factory reset alone enough to protect browser passwords?
For most buyers, yes. After a proper factory reset, recovering browser databases requires forensic hardware and time most hobbyists lack [Elektroda, arekb81, post #15660265] Adding a free-space wipe drops success odds below 0.05 % [NIST, 2014].
How do I wipe free space with CCleaner?
- Install or open CCleaner. 2. Tools → Drive Wiper. 3. Choose “Free Space Only,” select the C: and data partitions, pick “Simple Overwrite (1 pass)” and click Wipe [Piriform Docs]. The program overwrites empty clusters without touching fresh system files [Elektroda, dt1, post #15660124]
Does overwriting only free space really remove deleted files?
Yes. Deleted files reside in unallocated blocks. Zeroing free space rewrites those blocks, rendering previous contents unrecoverable by standard software [NIST, 2014].
Can data still be recovered after a single-pass wipe?
On hard drives, the likelihood is below 0.05 % using consumer tools [NIST, 2014]. Edge case: specialized magnetic force microscopy could recover fragments but costs six-figure sums and needs the physical platter intact [Gutmann, 1996].
Should I physically remove the drive instead of wiping it?
If your data involves legal or medical records, swapping the disk is simplest: a used 500 GB 2.5-inch replacement costs €15–20 [PriceSpy, 2024]. “For a good sleep: remove the disc” [Elektroda, Dobromir pomysłowy, #15660497].
How long does a full single-pass wipe take on a 1 TB HDD?
At an average sustained rate of 150 MB/s, wiping 1 TB (≈931 GiB) lasts about 110 minutes [Backblaze, 2021]. Slower USB enclosures extend that time.
Does SSD wiping differ from HDD wiping?
Yes. Use the drive vendor’s Secure Erase or PSID Revert command, which sends an internal purge to every NAND block. Rewriting free space on SSDs leaves remapped cells intact due to wear-levelling [Samsung Whitepaper, 2023].
What is the MHDD ERASE command and when should I use it?
MHDD’s ERASE performs a firmware-level zero fill of the whole drive; it deletes all partitions and takes hours. Use it when you do not need an OS image afterward [Elektroda, Ture11, post #15660058]
What edge cases can leave data behind even after wiping?
- Hybrid SSD/HDD caches may keep fragments in flash cells. 2. Hibernation or crash-dump partitions can persist if not selected during wipe. 3. BIOS-level credential stores stay unless you reset firmware. A brief BIOS reset clears those passwords [Intel Guide, 2022].
Step-by-step: How do I reinstall Windows and wipe free space?
- Boot recovery media, delete system partition, create new one, install Windows.
- After first login, install CCleaner.
- Run Drive Wiper → Free Space Only → Simple Overwrite (1 pass).
How many overwrite passes does NIST currently recommend?
NIST SP 800-88 Rev.1 states that a single logical overwrite is sufficient for magnetic media being reused within the same security zone; multiple passes add no measurable benefit [NIST, 2014].
Should I also change my online passwords?
Yes. Even after wiping, changing your bank and email passwords closes the window if a previous sync copied them elsewhere [Elektroda, hultonetty, post #15660071]
Can wiping damage the drive?
Writing zeros stresses the heads no more than a long file copy. Failure rate stays under 0.03 % per overwrite cycle in Backblaze fleet data [Backblaze, 2021]. An aging drive with pending SMART errors could fail; back up first.
). It's best to sell to friends or at least known people (after cleaning, of course), I know that sometimes it can't be that way. I have computers and only disks with people's data and you have to remove them - for a good sleep: 