First, enable window mode. The transition itself can occur by pressing the combination "Alt"+ "Tab"; installing the appropriate item in the options; via the console or via a parameter. The latter is done in the following way: you need to create a program shortcut, go to properties and in the target box after the file address to sign -windowed. This is a team-option, which each time will run the game in windowed mode, if supported.
"Pull" the window, "hooking" it around the corner. In other words, try to do so, how to change the size of any open folder. Please note that to change the scale to infinity, you can not – there is a minimum limit set by the program. However, this method is not always supported, so do not worry if it will not help.
Change the resolution. This is the number of pixels (dots), which takes the game window. Therefore, if internal resolution of the game will be the same as the value for the monitor, you will see only border around the edge of the crane and the window will still take up all available space. Outlet, obviously, are two: to reduce the indicators in the game or increasing in the system. So, if you set the internal value to 800*600 and the external at 1600*1200, the program will occupy only a quarter of the screen.
Download a newer version of the game. For example, in Super Meat Boy from the very beginning implied the possibility of switching to windowed mode, but it just didn't work on most systems. After installing a few updates and patches the problem was solved, and the game reacted calmly to reduce her assigned field.
Check the forums and the community of players. Especially this point is relevant for the online game: there are often more comfortable playing in multiple Windows for different characters, so users create their own programs and find a unique for each game to reduce the field to the desired size, if it is not provided by the authors.