Visual Basic Extensibility Reference
Contains all open or permanent windows.
Use the Windows collection to access Window objects.
The Windows collection has a fixed set of windows that are always available in the collection, such as the Project window, the Properties window, and a set of windows that represent all open code windows and designer windows. Opening a code or designer window adds a new member to the Windows collection. Closing a code or designer window removes a member from the Windows collection. Closing a permanent development environment window doesn't remove the corresponding object from this collection, but results in the window not being visible.