Adobe After Effects Issue With Composition Preview in Windows

I was trying to make my own smoke effect in After Effects, and the preview froze and wouldn't work so I would close it out. When I come back into the project, my compositions and layers are there but the window preview window is gone. I have retried three times from the very beginning ( makeing a new compositions and layers with effects applied to those layers), the preview stops working/freezes and when I close after effects and bring the project up, it preview window is gone.

I have a Dell with evo i5 processor, 16 GB of ram.

What do I do? How can I resolve this?