Windows 7: Is deleting a hard disk partition on Windows 7 installation secure?

Hi all,

I am preparing a laptop for sale, and have carried out a fresh install of Windows (booting from recovery CD). During this process, I selected 'Custom installation', followed by the hard disk partition containing my personal data and 'Drive options (advanced)', followed by 'Delete'. Is this a secure method of erasure or should I take additional precautionary steps before selling?

Thanks for reading.

To tell you the truth, it really depends. How paranoid are you? Deleting the partition should be fine as long as you did a Clean Install of Windows and then deleted Windows.old.
Windows.old Folder - Delete

But if you're really paranoid, you might want to also Quick Format...
Format a HDD or USB

...as well as using DBAN (Darik's Boot And Nuke). You simply load this tool onto a CD, DVD or USB and it securely erases all data from any discoverable hard drive until every single bit of data is permanently removed by overwriting all data on the disk with random numbers.
Darik's Boot And Nuke | Hard Drive Disk Wipe and Data Clearing

But unless you have very important and private data on that particular hard drive, I suggest doing a simple Clean Install and at the most, a Quick Format.

Deletion is not secure.

Formatting is not secure.

For all practical purposes, writing all zeroes to each and every byte is secure.

How do you do that?

You make a System Repair Disc.
You boot from the System Repair Disc.
You use DISKPART and its commands.

Make the System Repair Disc
| type System Repair | ENTER

Boot from the System Repair Disc
Put system repair disc into optical reader.
Power OFF computer
Power On computer
Immediatedly start tapping the F12 key.
Choose cd/dvd from the men
If F12 key doesn't work on your computer, then boot into your bios and set to boot order there so that Cd/dvd is first.

Use DISKPART
Sorry hit wrong key.
Next post will show how to use diskpart from the system repair disc

Use DISKPART to overwrite entire disk with zeros.
First you must get to a command prompt. Here's how:
GO TO A COMMAND PROMPT USING A SYSTEM REPAIR DISC

1) Insert System Repair Disc into optical reader.
2) Shutdown computer.
3) Boot up computer from the System Repair Disc
If your computer doesn’t boot from the optical drive, then
Immediately after pushing your Power ON button,
start tapping the F2 key to get to the BIOS to change the boot order

On some computers, Immediately after pushing the Power ON button, start tapping the F12 key and choose CD/DVD to change the boot order only for this time.
4) Wait while a mini-version of Windows is loaded and finally the SYSTEM RECOVERY OPTIONS dialog appears.
5) NEXT | SYSTEM RECOVERY OPTIONS dialog
will search your system for installed versions of Windows.
6) select the Use recovery tools that can help fix problems starting Windows radio button |
7) NEXT | Choose Command Prompt

========================================
========================================
USE DISKPART TO WRITE ZEROES TO ALL BYTES ON DISK
Enter following commands, each followed by hitting ENTER:
· DiskPart
· List disk (lists disks in your system)
· Select disk <numeral> (without the < and the >)
· Detail disk (info should let you know if you selected correctly)
· Clean ALL (your entire disk is being overwritten with zeros.
This can take a considerable amount of time.)
· EXIT (only type after Clean is finished. Exits from DiskPart)
· EXIT (this exits from the command shell)


Now if you haven't already, remove the cd/dvd and reboot your computer.