There are a couple of methods:

1) Use this tool called user2sid.exe, there is also a tool for doing the oposite

2) Use ldp.exe

   Start ldp.exe
   Choose Connection/Connect…
      (Type server or leave blank to connect to localhost)
   Choose Connection/Bind… to select user.
      (leave blank for current user)
   Choose View/Tree… to select base DN
      (leave blank for current domain)
   Browse to a user to see the attributes for that user

   Note: Different versions display SID differently

3) Use Adsiedit.msc

   Start Adsiedit.msc
   Browse to the user and view attributes