Snarl is a curious tool whose aim is to send messages to the user about the status of their Windows operating system. What Snarl does is send messages to the taskbar about the status of the connection to external devices, if the drives lack space, the status of batteries, etc.
Its interface is just a square in which you can read the messages. From Snarl you can also download plug-ins for various programs, like
Mozilla Firefox,
Thunderbird or
Songbird.
Snarl is free and hardly consumes system resources.