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my keyboard letters are mixed-up. i know this is a common problem.. but my problem still cant be solved..
my laptop model, LENOVO G480 (No numlock).
Fn+F8 --> dint work

This issue could occur if any key of the keyboard might have got stuck or due to some issues with the keypad.
Method 1: I would suggest you to try connecting an external keyboard to your laptop and check if you are facing the same behavior while typing.
Method 2: You may use the On-Screen Keyboard and check if face similar issue. Refer to the following link on how to Use the On-Screen Keyboard (OSK) to type
http://windows.microsoft.com/en-ca/windows-8/type-with-the-on-screen-keyboard
Method 3: I suggest you to boot the computer in clean boot and check if you are able to type properly. Clean boot process will help you determine which third party program/app that is causing this issue.
How to perform a clean boot in Windows
http://support.microsoft.com/kb/929135/en-us
Note: Please go through the section: How to reset the computer to start as usual after troubleshooting with clean boot of the Kb article to boot the computer in normal startup after fixing the issue.