Windows Uptime

Go to a command (dos) prompt -
Type 'net statistics server'

Look for the statistics since line - 

Microsoft Windows XP [Version 5.1.2600]
(C) Copyright 1985-2001 Microsoft Corp.

C:\Documents and Settings\user>net statistics server
Server Statistics for \\MYPC-123


Statistics since 7/30/2008 10:44 AM


Sessions accepted                  1
Sessions timed-out                 0
Sessions errored-out               0

Kilobytes sent                     0
Kilobytes received                 0

Mean response time (msec)          0

System errors                      0
Permission violations              0
Password violations                0

Files accessed                     0
Communication devices accessed     0
Print jobs spooled                 0

Times buffers exhausted

  Big buffers                      0
  Request buffers                  0

The command completed successfully.


C:\Documents and Settings\user>


Link : How to find windows uptime?