How secure is the Windows 8 "Reset your PC" function?

Question

Windows 8 has a feature to "Reset your PC" so that if someone needs to give their computer away, the recipient won't be able to recover data.

How secure is it?

Answer 1

That entirely depends on the option chosen during the use of the Reset your PC tool:

            

As you can see in the image above, the user is presented with two options:

• Just remove my files option is the faster of the two, and is meant to be selected when you're resetting your PC for your own personal use also after the reset.
• Fully clean the drive will take much longer to complete, and is to be used when you're giving your PC to someone else. It's supposed to prevent anyone from extracting personal information from your previous Windows 8 installation by using forensic file recovery tools, and make it safe to transfer your PC to a new owner.

Both options will literally install Windows 8 from scratch (which is good to know, as you might need to reinstall any custom drivers not included in your Windows 8 installation), but the latter option (Fully clean the drive) is supposed to securely^* erase your files, before it proceeds with reinstalling Windows 8. When the program finishes, it leaves your computer free of your personal data, and with a fresh copy of Windows 8, ready for the new owner.

---

^* One thing to add though, that I haven't been able to find any information on what specific method is used to securely erase files from the drive that this tool will reinstall Windows 8 on. Microsoft isn't really clear on it either. For example, in their page on How to restore, refresh, or reset your PC:

You'll be prompted to choose whether you want to erase data quickly or thoroughly. If you choose to erase data quickly, some data might be recoverable using special software. If you choose to erase data thoroughly, this will take longer but it makes recovering data far less likely.

Frankly, this lack of official information doesn't really fill me with confidence this process is entirely secure, and the recommendation to hire a certified Microsoft refurbisher in case of high risk data on their page on How to more safely dispose of computers and other devices doesn't help much either, basically telling us to buy more products to solve problems with the previous products we bought off them.

If you feel your best option is to secure erase your sensitive files on your own and not trust Windows 8's Reset your PC tool to do that for you, then here's a link to some apps on Windows 8 Downloads that should do that for you and are hopefully better documented, and here's another related question with some recommendations in the answers.