If you would like to reset your account to "factory settings", you can delete your data, custom fields and Interfaces. This will restore your account to the original state.
To do this, begin by deleting all of your data:
Click Data, then All Records.
Select Delete All Records from the Bulk Actions menu
Click Go
Delete your interfaces as follows:
Click Interfaces
Check to box at the top of the list of Interfaces
Click Delete in the toolbar
Delete your custom fields as follow:
Click Fields
Check the box at the top of the list of Fields
Click Delete in the toolbar
This will delete all non-system fields. The system fields, despite being selected, will remain.