Windows: After installing Moo0 WindowMenuPlus, right-click on any open window and you'll see new entries in the context menu that allow you to make the window transparent, keep the window on top of other apps, end the program, or kill the process.
WindowMenuPlus is free, and is a tiny utility that runs in the background while your Windows PC is running. As long as it is running, you can right-click any open window to kill the process, locate the program that opened the window in Windows Explorer, see the properties of the program, and more. You can even change the program's process priority or free unused memory from the right-click menu, not that we advise doing either.
The app can however be handy if an app is slowing your system to the point where you can't get to the task manager to kill it, or you have an app you want to keep on top of other windows or fade into the background. You can also control individual windows from the app's icon in the system tray.
Moo0 WindowMenuPlus is free, and supports Windows XP, Server 2003, Vista and Windows 7.