Use Task Manager Windows, if you are using Windows Vista, or Windows 7. It may be launched by pressing the keyboard shortcut CTRL + ALT + Delete.In these two versions of Windows on the tab "Performance" put a line with information about the operating time - look for it in the section "System".
Another method works in Windows XP, too.It involves the use of the system utility called systeminfo, for which it is necessary to open the terminal emulator command line.Press the key combination WIN + R and in the dialog box to run programs then type cmd.By clicking «OK» button you will be able to use the command line.
the command line type systeminfo.In order not to make a mistake, you can copy the name of the tool here (CTRL + C), then click in the terminal, right-click and select the context menu command "Paste".Then press Enter.In just a few seconds the utility will collect information about the operation of your operating system and displays it in a terminal window.
Scroll long list of report closer to the top and find the line "Time to Time" if you have installed in Windows XP.In this line, and while the system is placed in the current session.
Look for the string "boot time" in the case of Windows Vista, or Windows 7. Calculate the time of the system in this case, you may have to, subtracting from the current time period, which is specified in the line of the report found.
more detailed statistics on the time the computer can be accessed by using the software of other manufacturers.For example, if in the left pane, open the Everest section "Operating System", you can find a section called "Hours."It is placed not only the duration of the current session, but the last time the computer is turned off, the date and time of the first operating system is loaded, the total time and idle time for all this period, the length of the longest work sessions and downtime, etc.