How Do I Gain Administrative Access to a Second-hand Computer?


My dad bought a computer from a yard sale. The problem is that they forgot to take off the password. I’m logged in as a user, but not an administrator, so I don’t have admin privileges. How do I become an administrator?

This is frightening for many reasons.

It’s not you who should be scared. We’ll probably be able to get you into the computer. It’s the previous owner who should be concerned; it’s clear they didn’t take a few important steps before selling their computer.

You still need to tread very carefully. I’ll explain why.

Gaining access to a second hand computer

  • You may be giving away personal information when giving away a computer.
  • You risk exposing yourself to malware or worse when accessing data from a second hand computer.
  • The safest solution is to reformat and reinstall, not even trying to access existing hard disk contents.
  • If you must, try a password reset tool.
  • Alternately, remove the hard drive and connect it to a different computer as a secondary drive.

Seller beware

The problem for the original owner is this: they’ve given away or sold the computer … and all of the data on it.

How do I know this? Because it still boots into Windows. It’s clear they did not take the extra step to securely delete all of the data on the hard drive. We hear stories all the time of second-hand computers that are sold or discarded with a tremendous amount of sensitive personal data still on the machine.

They may think they’ve deleted the files they care about, but as I’ve discussed in many articles in the past, there are often sensitive remnants in other places, and even deleted data can sometimes be recovered.

So lesson #1 is for whoever sold the computer in the first place: securely erase your data, or you run the risk of the computer’s new owner having access to all of it.


Buyer beware

Do you know what you have?

I mean, do you really know what you have?

How do you know the machine you just received isn’t chock-full of malware?

For all you know, there are viruses, trojans, spyware, ransomware and more on that machine, just waiting for you to do something: connect to your local network, share files with other machines, or log in to your bank account. They’re waiting for the opportunity to propagate, compromise, destroy, and generally cause havoc.

I’m not saying this is the case; I am saying you can’t know that it’s not.

You have no idea how safety-smart the previous owner of that computer may or may not have been. You have no idea what’s on that machine. You have no idea what you have … not really.

The right solution

So lesson #2 is for you, the person acquiring a second-hand machine by whatever means.

The right thing to do is to ignore anything that’s on the hard disk, get a Windows install disk, and reformat and reinstall Windows from scratch. It’s the only way to be certain you know what is — and perhaps more importantly, what is not — on the machine.

It’s the “right” way for two reasons:

  • You’re not even going to try to access or recover the previous owner’s data.
  • You’re not going to suffer from any infections or malware left behind by the previous owner.

That fact that the previous owner didn’t know enough to securely erase their data doesn’t bode well for their security habits, either.


Getting access anyway

I know, I know, sometimes people are curious or “adventuresome” (perhaps a synonym for foolhardy?) and want to see what’s on the existing hard disk.

Fair enough. There are two approaches.

  • It may be possible to gain access by downloading a password reset tool and booting from it. I’ve covered this in: I’ve Lost the Password to My Windows Administrator Account, How Do I Get It Back? While this approach doesn’t always work, when it does, you simply set the administrator password and reboot into the installed operating system. You’re in.
  • Remove the existing hard drive, place it in an external enclosure, and connect that to a different PC. This will at least let you examine the hard drive’s contents.

As I’ve also said before, if you have physical access to a machine, then it is not secure. That works in your favor here.

Just be sensitive to the data that you might find — and know you may be dealing with malware or other security issues you may not be able to see or recover from.

Originally published as How Do I Gain Administrative Access to a Second-hand Computer? on Ask Leo!