Hi Nurul. I'm Greg, an installation specialist, 10 years awarded Windows MVP, and Volunteer Moderator, here to help you.
They do not make it easy when you forget your password, or else anyone could say they're you and get into your account. You should first try changing the password. If it's a Microsoft account password and you set up a security email or phone number then you can change the password easily enough in your online account here:
https://support.microsoft.com/en-us/help/402683...
If not you have to go through account recovery:
https://support.microsoft.com/en-us/help/17875/...
If it's a local account you can change the password from the sign-in screen if you set up test questions for this purpose:
https://www.windowscentral.com/how-add-security...
You can also enable the built-in hidden Administrator used only for emergencies as shown here:
https://www.isumsoft.com/it/enable-hidden-admin...
Sign into it to create a new Local Admin account in Settings > Accounts > Family & Other People > Other, as shown here:
http://www.howtogeek.com/226540/how-to-create-a...
Sign into the new account, test if the problem persists, if not then move your files over, test that all programs work or else reinstall them, then when ready delete the old account in the same place, and hide the built-in Admin account.
You can then change it to your Microsoft account if desired:
https://www.tenforums.com/tutorials/5375-switch...
If these all fail then you may need to reset your PC, saving files. In order to avoid the need for the password you forgot you may need to create bootable media to access Reset or do the Clean install:
To create Windows 10 Installation Media on another PC install Media Creation Tool and follow the directions here:
http://windows.microsoft.com/en-us/windows-10/m.... Uncheck the box for Recommended Settings to choose the exact version and bit rate for the target PC only.
Insert media, boot it by powering up PC while pressing the BIOS Boot Menu Key:
https://www.sysnative.com/forums/hardware-tutor...
If the media won't boot you may need to enter BIOS/UEFI Setup (pressing key given in chart in link above) to turn off Fast Boot or Fast Startup first.
Choose the boot device as a UEFI device if offered, on second screen choose Repair Your Computer, then Troubleshoot Options to try a Reset.
If that fails choose Install Now, then Custom Install, then at the drive selection screen delete all partitions down to Unallocated Space to get it cleanest, click Next to let it create needed partitions and start install - this makes it foolproof. Everything needed to get the best possible Clean Install is here:
http://answers.microsoft.com/en-us/windows/wiki.... It is a better install than any amount of money can buy and a great learning experience that will make you the master of your PC because you will learn what works best and how to apply it with your own hands.
If you have files that aren't backed up you can use the same bootable media to try to rescue your files using these methods:
http://answers.microsoft.com/en-us/windows/wiki...
A suggestion for creating a complicated password that you'll remember: a [childhood street address] + [phone number] that doesn't exist any longer and only you remember for life.
I hope this helps. Feel free to ask back any questions and keep me posted. If you will wait to choose if I solved your problem, I will keep working with you until it's resolved.
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