It is included in the Windows registry, which you can edit with the registry editor. Before you do anything that I suggest below, you should become familiar with the Windows registry and the problems that can occur when editing it. You will find this discussed many places on the net, for example: What is Registry Editor? - Windows Help
You can launch the registry editor by doing the following in Windows:
Start > Run > type "regedit" > OK > Yes (when prompted to allow changes)
You should see a left and right hand panel and you'll want to navigate to the registry entry as shown below:

If there is an entry for "dopacity" in the panel on the right in the Name column, you should see that it has a value (Data column) less than 1. You can either change it to 1, or remove the dopacity key altogether.