Here are a few more topics for you to search on google.

Social engineering
Password policy (How to make and protect a good password)
Physical protection (keeping unauthorized people away from the computer or servers)
packet sniffers
Encryption
VPN (Virtual Private Network)
Group and Users policies (setting the permissions on different folders for groups and users)

Those are just a few. I could go into a lot more. Is this going to be about a lone computer at home or a computer that is part of a network?