Need to reinstall Windows version I've already purchased? Where do I do this?

My DJay Pro for Windows tries to come up but then disappears. It does not show in Program list now either.
I need to reinstall and install it again. How do i do that? All I see is the link to buy it?? I’ve already bought it!

Perviously, it would crash all the time. Also, When I use my mouse cursor it would hang on the slide mixing bar.

Please help!

-Greg Holland