We tested Express Accounts but decided not to use it. I'm pretty sure it comes with Express Invoice, so it would be redundant to purchase both. Here is the page that answers that specific question: http://www.nchsoftware.com/accounting/kb/1551.html It is in their FAQ part of the Express Accounts info page.
Have you been testing in your company name? If not, you could start another company, which would have everything start at zero. If you have, you can delete all the entered info, but I would recommend you double check Inventoria to make sure everything returned to zero, or to the beginning levels of your inventory.