This time, it's an older game, from at least 10 years ago.
The platform was windows 95. The game itself was freeware or shareware, I cannot recall. It was an action game similar to DROD, in which you piloted a tank that fired bubbles. It was turn based, and you were able to upgrade your tank as you progressed. I cannot remember the plot exactly, but it was a very long game. It played in a window, and had buttons you could click on to move and numpad support.