Process Explorer - The top window always shows a list of the currently active processes, including the names of their owning accounts, whereas the information displayed in the bottom window depends on the mode that Process Explorer is in: if it is in handle mode you'l…
Winspector Spy - Have you ever used Spy++ that comes with MSVC?
What's Running - What's Running is a product that gives you an inside look into your Windows system.
Window Detective - Window Detective is a programmer's tool used to "spy" on an application's windows...
Security Task Manager - Advanced process viewer that provides detailed information about programs and processes running on the computer (e.g. file name, directory path, description, security risk rating).
WinSpy - Retrieve window information.