Reset your Windows password
Ubuntu can also edit your Windows user account passwords, which is great if you've forgotten your Windows password. We tested this on a modern Windows 8.1 Update system and it worked perfectly. We'll be modifying the Administrator account here--after you unlock it and clear its password, you can log into Windows as Administrator and reset your other passwords.
Open a terminal by clicking the Ubuntu logo in the top-left corner of the launcher, typing Terminal, and pressing Enter. Run the following commands to install the password-changing utility you'll need. (If you've already run the first two commands, you don't need to run them again--just run the third one here.)
sudo add-apt-repository "deb http://archive.ubuntu.com/ubuntu $(lsb_release -sc) universe"
sudo apt-get update
sudo apt-get install chntpw
Be sure to open the file manager from the launcher and click your Windows drive under Devices to view its contents if you haven't yet. This will "mount" the drive and make it available in the terminal.
Next, start typing the following command into the terminal, but do not press Enter:
Now, press the Tab key twice. You'll see an alphanumeric label that corresponds to your hard drive. Type the first few characters and press Tab again to automatically fill the label in. Now type /Windows/System32/config so you end up with a command that looks like the following, and then finally press Enter:
Run the following command and press Enter to start modifying the Administrator account. SAM is the name of the Windows system file containing the hashed user account passwords.
sudo chntpw SAM
If your Administrator account is locked--and it is by default--type 4 at the prompt and press Enter to unlock it. Type y at the confirmation prompt and press Enter to confirm.
You'll have to run the sudo chntpw SAM command again to get back into the program. Type 1 and press Enter at the prompt to clear the Administrator's password and make it blank. Type y at the prompt and press Enter to confirm again. Important: Do not use the change password option here, as it could cause problems.
You can now log into Windows with the username Administrator and a blank password. From there, you can open the Control Panel and reset other user account passwords. (Worried about other people doing this to your Windows system? Set a BIOS password to ensure they can't boot to removable media and mess around with it.)
Scan for malware
Rootkits are a nasty type of malware that burrow deep into Windows and start at boot-up, pulling strings in the background so they're invisible to antivirus programs and hidden even from the Windows Task Manager. Even if you have bog-standard malware, it's often easier to remove malware from outside Windows. Antivirus companies often make dedicated antivirus boot discs you can use to scan your system from outside Windows, but you can do this all from within Ubuntu.
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