Three times recently the clock on my PC has overnight reset to a time in the year 2003. This is only discovered when I boot up and find several programs will not work until the time is reset correctly. There has been a gap of two or three weeks between each of these incidents. I always shut down my PC at night but leave it on standby, so it has power available 24/7. Can anyone suggest what is causing this problem and how to rectify it please?