Wed 23 May 2007
Microsoft has an article on their website discussing this issue. To sum it up, it doesn’t really matter so long as your computer is set to hibernate after a reasonable amount of time. If your computer is not set to hibernate then leaving it on means it is costing you in power. To do this go to the Start menu and click Control Panel, then Power Options, then under System hibernates: select After 45 mins or which ever setting is best for you.
If you would rather turn it off but are concerned that frequently turning your computer on and off will wear it out you needn’t worry. Today computers are can handle 40,000 on off cycles, which is a number you are not likely to reach in the computers expected useful lifetime (5-7 years).
To view the Microsoft article click here.