Determine the current system up time

Uptime is a simple command line tool that analyzes a single server for reliability and availability information. It can work locally or remotely. In its simple form, the tool will display the current system uptime. An advanced option allows you to access more detailed information such as shutdown, reboots, operating system crashes, and Service Pack installation.
You can download uptime.exe from here:
http://download.microsoft.com.../uptime.exe
Download and save this file on your hard disk. You can then run uptime.exe from a command prompt. Type cmd.exe in Start, Run  and uptime.exe
You'll see the output like this:
\\SUPERCOMPUTER has been up for: 0 day(s), 0 hour(s), 49 minute(s), 6 second(s)
Uptime Reliability and Availability Information Tool
Uptime.exe Tool Allows You to Estimate Server Availability with Windows NT 4.0 SP4 or Higher