The initial setup of your computer with the proper protections and settings is the most important thing you can do to ensure its performance and your personal security.  Below is a quick list of thing you need to do when you initially purchase your computer.  Unfortunately computers rarely come out of the box with the proper setup.

1.  Update your operating system with the latest patches

2.  Install Antivirus software

3.  Install Anti Spyware software

4.  Un-install unnecessary software that is installed when you purchase your computer

5.   Install the software that you need on the computer

6.  Set your operating system, antivirus, and spyware software to update at different times while you computer is not in use

7.  Disable guest user account

8.  Set strong passwords for all user accounts

9.  Disable unnecessary services

10.  Set screensaver time options

11.  Set screensaver to require password on wake up

12.  Set power options to turn off monitor after 30 minutes (or whatever your personal preference is)