My business partner is on vacation, and I need a file that's on his computer. Unfortunately, there was a power failure, and now I need his system password to get the PC up and running again. But I don't know his password. But first you have to sit through a lecture. Parents may prevent the kiddies from viewing inappropriate Internet content, a sensitive file can be shielded from the office busybody or, as in this case, access to the entire PC can be restricted.
Some passwords are easy to defeat, others less so, and still others all but impossible.
Fortunately, much of the assistance you seek is already public information. For example, the system password that must be entered simply to get the PC to complete the bootup process. If you've truly forgotten it, assistance should be no farther away than the user's manual. The manual will describe a tiny jumper block on the motherboard typically with three inline pins and a jumper across pins 1 and 2. With the power off, move the jumper to pins 2 and 3, then restore power.