CERT is one of my favorite websites in promoting security best practices. This is an excellent article promoting the best practices for protecting your home PC.
Article: The Goal of Computer Security or What's Yours is Yours Until You Say Otherwise!
Simply stated, the goal of computer security is this: keep your computer-based possessions-your computer system (CPU cycles, memory, disk space, and Internet connectivity and speed), the software you've purchased, and the files and folders you've created-yours unless and until you explicitly give them to others.
And this concept isn't new. It's what you've been doing for years with most all of your other possessions. For example, the doors on your house have locks and you use them. So do the windows and so does your car, and you use them too. You don't give the keys to anyone who asks for them without a really good reason, or perhaps never at all. You don't leave your CD player and your CDs out for all to use and perhaps take. You don't store your financial or your personal medical records on your front porch.
Best Security Practices for the Home PC - Summary of Topics Covered
Task 1 - Install and Use an Anti-Virus Program
Task 2 - Keep Your System Patched
Task 3 - Use Care When Reading Email with Attachments
Task 4 - Install and Use a Firewall Program
Task 5 - Make Backups of Important Files and Folders
Task 6 - Use Strong Passwords
Task 7 - Use Care When Downloading and Installing Programs
Task 8 - Install and Use a Hardware Firewall
Task 9 - Install and Use a File Encryption Program and Access Controls
Below are some additional related articles from the CERT website
Best Security Practices for Home Networks
Before you plug that new PC into the Internet
Security of the Internet