A man goes to see his doctor because of a problem he is having concerning his memory. The man tells the doctor "I have been having lots of problems remembering things that happened in the past couple of hours, you know, my short term memory." The doctor replies "How long has this been going on?” The puzzled man looks back at the doctor and says "How long has what been going on?"
Computers are like air conditioners. They work fine until you start opening windows.