Windows uptime is the measure of the time the computer is continuously up and running.
In vista it is very simple to find out the uptime.
Go to task manager (by pressing CTRL+SHIFT+ESC) and select performance tab
In the system you can find the windows uptime
In windows XP we can find out the uptime using system information
Start –> Run type cmd and click ok
In the command prompt type ’systeminfo’ without the quotes and press enter.
This will give the list of details, one of which is the System Uptime.
This will also work in windows vista.