Windows 7 gadgets are small applications that run on your Windows 7 desktop and can do all sorts of tasks.
There are Windows 7 gadgets that act as calendars, search interfaces, Twitter interfaces, battery life indicators, you name it. There are even gadgets that can keep track of your system resources, like these Windows 7 gadgets.
Downloading and installing a Windows 7 gadget to your desktop is really easy, but if you've never done it, these instructions should help:
Download the Windows 7 gadget file.
Most Windows 7 gadgets are freely available from various websites.
Execute the downloaded GADGET file.
Windows 7 gadget files end in the GADGET file extension and will open with the Desktop Gadgets application.
Click the Install button if you're prompted with a "Publisher could not be verified" security warning.
Most Windows 7 gadgets are created by third party developers that do not meet Microsoft's identify verification requirements but this does not necessarily mean that there is any security concern.
Configure any necessary gadget settings.
Depending on the Windows 7 gadget you installed to the desktop, there may be certain options that need configuring like gadget opacity, number of CPUs to monitor, your Twitter account, etc.
Not a Windows 7 user? See How Do I Install a Windows Gadget? for instructions specific to your version of Windows.
Desktop gadgets are not supported in Windows XP and older Windows operating systems.
If you remove a gadget from the Windows 7 desktop, the gadget is still available to Windows, it's just not installed on the desktop.
To add a previously installed gadget back to the Windows 7 desktop, just right-click anywhere on the desktop and click on Gadgets. A window will appear showing all available Windows 7 gadgets. Just drag the gadget you want to the desktop.