JSI Tip 5471. SidToName freeware Will decode a SID at a specified machine into a user-friendly username.

Downloads
SidToName.zip

Download SidToName, which will decode a SID into a user-friendly username.

The syntax for using SidToName is:

sidtoname SID \[ComputerName\]

where SID is the Security IDentifier you wish to enumerate, and ComputerName is the optional computer name where the SID resides. If ComputerName is omitted, the local computer is used.