There is a known issue with the Lego Mindstorms Robitic Invention System IR Tower and computers with CPU's that have hyperthreading enabled (eg. socket 478 based cpu's). This error causes the computer to freeze up when attempting to download programs from the IR tower to the brick. In case any other students have problems with this I thought you might like to know that the fix can be found at the URL: http://www.lego.com/eng/service/downloads/patches/Tower164.zip