To reset the admin password for nopcommerce, the easiest way to do so is click "Login" on the top of your NopCommerce installation, then click "Forgot Password".
When you do not have access to the email address of the account, you can simply do the following:
1) Create a new account on your NopCommerce site
2) Remotely connect with MSSQL to the database of your NopCommerce
3) Open the "Customers" table, find the new user you made, and modify "isadmin" and "ismoderator" to "true". This will set the new user you made as administrator.
Some of the table names or column names may differ from version to version, but the steps will always be very similar. Now that you have the right user/pass.