Dear Jon,
If you are looking to change the username and password that Checkbox uses to connect to the database jrjespersen has it. This value is stored in the web.config file. You will want to edit the connectionStrings node. It looks like
<add name="DefaultConnectionString" connectionString="server=pwiesner;database=Checkbo x_4.4.1.14;uid=USERNAME;pwd=PASSWORD;Application Name=Checkbox Survey Server;" />
You will also need to make sure that the new SQL account has access to the Checkbox tables and data.