what is a small note that display to provide about a button or describe the screen element
Usually, this is called a "tooltip."
The page that displays the icons when you turn your computer on is called your home screen. Some people do call it the main screen as well.
the desktop
menu button
The Toolbar.
Your question is not very clear. If you are referring to the screen (monitor) of the system, it displays the graphics and the interface. If you are referring to the actual computer (most often called the tower) it holds the hard drive, video & sound cards, all of the wires, processors, and is where the power button is located.
bitmap fonts
The portion of the screen that displays when windows XP is loaded is called the Desktop. It features icons for different programs, the Taskbar and the Start Button.
Its Called The Computer, The Top Part Is Called The Screen The Metal Box Is Also Called The Hard-drive
log off or shut off computer
When you say button, the start button is called the power button and it turns power on/off. There is no start icon as you see on a windows computer. On Mac the equivalent is the Finder icon.
I think you are referring to the 'Task Bar'.
A computer screen can be called a few things. Most commonly, they are referred to as "Computer Monitors". They are also called "Computer Displays". Sometimes, they are referred to by the technology they employ to display an image, or by other physical characteristics of the device. For example, sometimes the abbreviation CRT is referring to a computer monitor. CRT stands for Cathode Ray Tube. CRT monitors are very similar to older televisions. Sometimes, monitors are called Flat Panel Displays. This usually means that it is an LCD monitor.