If your running Windows at home there are a few things that can help you secure your computer:

• Keep your operating system up to date.
• Keep your web browser up to date (update any software when patches become available)
• Install an up to date virus scanner and update virus definitions as soon as they become available
• Log into windows as a regular user and only use the Administrator if you want to install or configure your operating system
• Buy a router and configure a local network at your home. Make sure to set a default admin password and enable encryption (for a wireless network)