Instructions
Open Notepad. You can find a shortcut to it in the "Accessories" folder of the Windows Start menu.
Click on "File" and select "Open."
Navigate to the following folder by using the file browser:
C:\Program Files\Rovio\Angry Birds
Then double-click on the "config.lua" file to open it in Notepad.
Locate the line which contains "Width = XXXX", where XXXX is a numerical value. Replace XXXX with "1024". Then locate the "Height = YYY" line and replace YYY with "600".
Click on "File" and select "Save." You should now be able to launch "Angry Birds" again.