WinGhostifier is a small utility that will let you set any window transparent in Windows 2000/XP or higher. It has no GUI (graphical user interface), only an icon in the system tray, so it uses almost no memory. I tried to make it as small as possible.

The program is a single EXE. It won't install any DLL, write any INI file or screw up your registry. To remove it, simply delete the EXE from your system.