Sorry if it's a stupid question, but I want to know if I can pick which files to back up on my MacBook (snow leopard). I just don't have much space on my external hard drive. I know I should back up pictures, movies, music, documents, etc... but do people usually need to back up their entire HD? I want to know if there are files I can skip, such as stuff in the "system" like the Library folder etc.?