The toolbar at the top of any program you use that contains the "File," "Edit" and "Help" menus (among others) is often called the "Menu" toolbar. It was given this name due to the fact that it contains a number of drop-down menus that give you further control of the program. If this toolbar has disappeared, you don't need to worry -- it's not gone permanently, it's just been accidentally turned off. To get it back, you merely need to turn it back on.
Open the program that has the disabled "File" toolbar. To open a program, double-click on its shortcut icon on your desktop. If you have lost the "File" toolbar while working with Windows Explorer, simply open any folder on your computer to open the Windows Explorer program.
Right-click anywhere on the top portion of the program window that is not occupied by some kind of button or drop-down menu. This will bring up a menu containing a list of toolbars that are installed for that program.
Click on "Menu" toolbar to put a check next to its listing. Note that some programs may call this toolbar something different, with alternate names being "File" and "System" toolbar. Clicking on the toolbar will re-enable it within the main program window; this will return the "File" menu (along with all the others) to its normal position at the top of the program.