I didn't understand the graph properly but if what I understand is correct then the graph was sort of hilarious. Are you telling me that Win XP is the second most secure operating system? I haven't used Vista so I can't judge but I think this graph looks like it was made by the microsoft people. And it shows Ubuntu with the most number of problems! You gotta be kidding me... I think you forgot to take into account the number of virus that exist in each operating system...