Because most versions of Windows do not include a method of password protecting your files and folders, this page provides steps for encrypting files and folders instead. To password protect your files and folders in Windows, you need to use a third-party program.
Tip:-Before password protecting any document, you may want to create a backup of the non-password protected files and folder in case you forget the password in the future.
Microsoft Windows Vista, 7, 8, and 10 users
Unfortunately, Windows Vista, Windows 7, Windows 8, and Windows 10 do not provide any features for password protecting files or folders. You need to use a third-party software program to accomplish this.
If you want to encrypt a file or folder, this can be done by following these steps:
Select the file or folder you want to encrypt.
Right-click the file or folder and select Properties.
On the General tab, click the Advanced button.
Check the box for the "Encrypt contents to secure data" option, then click OK on both windows.
Note:-
If the "Encrypt contents to secure data" option is not selectable and grayed out or you do not see the option at all, you likely have a Home edition of Windows, which does not support this feature. It is also possible that the hard drive where the files are located is not formatted as NTFS, as this is a requirement for the encryption feature.