2 ideas come to mind. First your explorer.exe isn't running properly (which is what displays all the parts of the Windows Interface). Or your icons and taskbar have been set to 'hidden' mode.
Are you able to right-click on your desktop? If so right click>Arrange Icon By>Make sure there is a 'check' by 'Show Desktop Icons'. If this brings them back move your mouse along all 4 edges of the screen to see if the taskbar pops up anywhere.
OR
Try ctrl-alt-del>choose Task Manager>File>NewTask>type in explorer.exe and see if that brings the stuff back.
Press Ctrl+alt+del and press task manager. If your using windows xp it may automatically come up. Click file, new task and find explorer.exe and it should work. Just search your computer for explorer.exe.