For anyone with a computer/computers at home I do encourage several things.
1. Make sure you need to log into the OS. In an IBM style (windows) pc you can also set a BIOS password when you even boot the computer. One can get around it but you have to know how.
2. On a mac make sure you do a back up with time machine or just the files you want to protect/save. for me i would die over lost pictures and music. i’m moving most of my simple documents to online sources since they don’t take up much space. On a PC there is software to make backups. You can leave it connected to the computer or just do daily/weekly/monthly backups and put the hard drive some place safe.
3. if you leave passwords in files on the computer you can protect word/etc files with passwords. you can also just have mnemonics to help remind you of the password instead of typing down the actual password.
4. you can take things a step further and on a PC with windows 7 (pro and ultimate) turn on bitlocker to encrypt the harddrive so even if it put into a new computer they can’t access the info. On a mac you can turn on filevault.
BUT!!!! You must remember the password / key (save it online maybe or stick in a safe deposit box) or you might lose EVERYTHING if you can’t remember the password/key. apple can store your key with three challenge questions.