You have a mismatch between your keyboard and the setting for it in laptop. This is usually a case of English UK and English American being confused.
An American keyboard has the @ sign above the number 2. An English keyboard has it above the apostrophe, to the right of semi-colon. Insert the @ sign by using the one of these which does not have the @ sign displayed.
To bring the keyboard and laptop into agreement, you need to change the keyboard settings. In Windows 7, press Start, select Control Panel and Region and Language. Then select Keyboards and Language and Change Keyboards. you will now see the default keyboard setting displayed. Select Add and toggle down to English (United Kingdom) or English (United States) and add whichever is not your default setting. Then change to default to the version you have just added.