King Reza: I know of two scenarios in which the taskbar disappears:

a) Explorer crashes
b) It is hidden

If explorer crashes, it usually just restarts. and if the taskbar is hidden, it usually reappears when you move your mouse to the bottom of the desktop. You can hide/unhide the Taskbar through Start -> Setting -> Taskbar&Startmenu.

If your taskbar is not hidden, and explorer doesn't recover, go into the task manager (Ctrl+Alt+Del -> Task Manager) and start explorer (click "new task" and type "explorer", then hit enter)

Gordon Shumway:Thanks for the reply.  No it's not hidden.  I already checked that.  And I did what you said, running explorer and stuff, and it didn't work. 

King Reza: That's bad news :(

Is explorer running then? If it is, you can see "explorer.exer" in the list on the "processes" tab of the task manager. Also, if explorer is running, hitting WinButton+R should show the "Run" dialog.

King Reza: CAUTION - this might be a stupid question:

Have you tried rebooting? ;)