You can see what products you already own logging into the Topaz Labs website and selecting Account -> Purchased Products
On that page you will see all of the products that you own. Each product comes with a handy link to the downloads page where you can find your installer.
You will be able to see what products you currently have an active trial open for at the top:
Followed by a table showing all of the classic Topaz Labs plugin style products you have:
Followed by a table showing all of the Topaz Studio adjustments that you own:
You can see what adjustments you have in Topaz Studio by selecting the Adjustments Menu or using the Add Adjustment button in Topaz Studio
Followed by a table of all the standalone Topaz products you own. These are applications that are not plugin only, they can be run as standalone applications. They are not Adjustments inside of Topaz Studio.