You must download Altera Quatrus 2 Web Edition and Modelsim Simulator From:
http://dl.altera.com/?edition=web&platform=windows&download_manager=direct
You must install Cyclone IV device support also for DE0-Nano Development and Education Board
If you want to buy this board, you can find it here: http://market.cizgi.com.tr/product/education/altera-de0-nano-academic