You should click "Start">"Xilinx Design Tools">"ISE Design Suite xx.x">"EDK">"Xilinx Softwate Development".
After this a pop-up will appear.
In this pop-up you should choose the SDK_Workspace desired.
After this the SDK will open.
If the version of the SDK is higher than the version of the project opened you should follow the instrucyion and refres the demo .c and .h files.
Overview
Content Tools