What is a "test account?"
This is an account that you set up to be used for troubleshooting. If you log into this account (more about how to do that later) and the problem is gone, something in the original account (i.e., your home folder) is to blame. If the problem exists in both accounts, then the cause lies outside the home folder. For example, a corrupt preference file in your main account can cause problems; those problems will not occur in a test account because its preference files are at defaults.
To set up such an account, go to System Preferences > Accounts. If the padlock icon is locked, click it to unlock it (you'll be prompted to enter your administrator password). Then, click the + icon at the bottom left of the screen, just above the padlock icon. Follow the prompts and be sure to check the box to allow the user to administer the computer.
Once the account has been established, it will appear in the left column of the Accounts preference pane. To log into that account, click the Apple menu (upper left of the screen) and select Log Out. A login window will appear. Select the new account and, if necessary, enter the password that you established for that account. In a moment, a new desktop will appear at factory defaults, as well as everything else. None of your custom settings will apply and you want to keep this account at factory defaults for testing.
When finished, log out of the test account and into your regular account.