How to completely remove the data's from databases

Hi all,
In the purchase order I have did some sample Purchase order’s, Production order’s, Lead, invoice and receipt. I need to empty the data’s and use it with live data’s.
When I start set the live data’s it continues with previous deleted data number. How can i start with the 1, 2, 3… but the naming series number should be the same such as LEAD 00001.

In the purchase order I have did some sample Purchase order’s, Production order’s, Lead, invoice and receipt. I need to empty the data’s and use it with live data’s.

Goto Company and click on ‘Delete Company Transactions’… but you will have to delete master data manually(customer,supplier etc)… and also you will have to reset the counters manually i guess…

Better to create a new site using bench!