Final answer:
The accounts in question most likely belong to the 'Users' group on a Windows 10 computer, as they can sign in and work on files but cannot install new software, which requires Administrator privileges.
Step-by-step explanation:
The accounts that allow users to sign in, work on files, and save them, but not to install new software on a Windows 10 computer, most likely belong to the 'Users' group. Accounts in the 'Users' group have the ability to perform common tasks but do not have the necessary permissions to perform administrative actions such as installing software, which is a task reserved for the 'Administrators' group. The 'Power Users' group that used to exist in earlier versions of Windows typically had more permissions than standard users but less than administrators, however, this group has been phased out in modern versions of Windows. 'Device Owners' is not a standard user group in Windows 10.