(and is REALLY NECESSARY in order to offer more than a guess) that you take the time to tell us the type of computer (desktop, laptop, mainframe, etc.) and the Operating System (Unix, BSD, DOS, Mac version nnn, Amiga, Linux, QNX, Windows version and SP level if applicable) as all are different.

On the assumption that yours is a Windows based PC open the Control Panel then the Keyboard applet. Now make sure that English US (or whatever you originally used) is selected as the language and keyboard as follows ...

As a user with Administrator rights click Start, Control Panel, Keyboard applet icon.

Click Hardware tab, ensure keyboard Type is selected and click Properties.

From the Date, Time, Language and Keyboard option and Regional Options tab, set Location to United States and click OK.

Right click the EN icon on the Task Bar.

Select Settings...

Select English [United States]