If your Windows XP PC is left on for extended periods or it has been left unattended for any length of time then it may be useful to know the ‘Uptime’ or how long it has been since the last reboot. To find out you need to open the Command Prompt window by typing ‘cmd’ (without the quotes) in Run on the Start menu. After the flashing prompt type the following command. Be careful, it’s case-sensitive, watch for the spaces and quotes and the vertical line ‘|’ or ‘pipe’ symbol is usually on the backslash key:
systeminfo | find "Up Time"
Press Enter, Windows will chunter away for a few seconds and then display the Uptime, in hours, minutes and seconds. If your PC is connected to a network you can find out how long it has been online (usually the same as Windows Uptime) by right clicking on the Network icon in the System Tray (next to the clock), select Status then the General tab.
In Linux, you just type "uptime" to know how long it has been since the last reboot.
Update 11 April 2006 :You can also try this ...
Open a command prompt and type NET STATISTICS WORKSTATION
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