Everyone seems to want to hack and remove passwords. I want to ADD one to prevent nosey housemates from using my computer. I do not have a physical key to lock it up with. So how is it done? Any references, links, etc. would be appreciated.

Info: 2nd-hand HP 120MZ Intel Pentium.
Per Windows System info: BIOS by Phoenix Technologies & Bus type PCI; per POST info: System BIOS version GM.05.03 (whatever that means?)

Thanks in advance.