If the account is a Trial Account of Salesforce and then any time you can decide to delete all the data including the sample data. Your trial account data is stored in the Salesforce trial organization.

To get the Delete button in the Account follow the instructions:

• Go to the Setup ->Data Management | Delete All Data.
• Salesforce will request you to enter text to state that you understand all data will be deleted:
• Click on the Submit button as shown in the preceding screenshot to complete this process.
• Note: This feature is only available during the trial period.