Most office employees do not shut down computers at night – they just lock the workstations and switch off the monitor but that doesn’t stop the computers from consuming power.
According to estimates, 30% of all office PCs in the US are left on all night while 18% of office workers in UK admit that they have never switched off computers over night or at weekends.


            So do you remember the exact date or time when you last switched on the computer ? Here’s a simple DOS command to help you out: systeminfo | find /i “boot time”

             This will show the time when you last rebooted the computer. 

Subtract that from the current date-time to know for how long you have been running the computer.
windows-task-manager Alternative, you could start Windows Task Manager (Alt+Ctrl+Del), switch to the Performance tab and you should see a field that says “Up Time” – that’s even more convenient but some computers have Task managers disabled.