Hi,
To find out the name of the account associated with an SID you can (works with XP may not work with later versions of windows server though):

  1. Open Registry Editor and navigate to:

    HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion \ProfileList
  2. Under the ProfileList key, you will see the SIDs. By selecting each one individually, you can look at the value entry and see what user name is associated with that particular SID.

http://support.microsoft.com/kb/154599

Cheers
Muarcu