Symbols ” and @ have replaced themselves on my keyboard

How to revert that and what is the cause?
Answer #1
http://lmgtfy.com/?q=%22+and+%40+have+changed+on+my+keyboard
Answer #2
change regional settings in control panel for win xp
Start
Control Panel
Date, Time, Language, Regional Options
at the bottom of that menu, select “Regional and Language Options”.
choose locale you are in uk/us
reboot
Answer #3
If the @ should be on the 2 key then you need the US keyboard layout. If it’s supposed to be next to the # key near the enter key then you need the UK keyboard layout.
You’ll probably also find that you’ve lost the �� on shift-3