When working in a fat client environment and you need to make a change to a users local machine registry key you can connect to the remote registry and make your changes. In a thin client environment, all users share the HKey_LocalMachine key and each users HKey_Users key is listed individually by SID.

To determine which user the SID belongs to you can check the APPDATA key under HKey_Users\SID\Volatile Environment.

APPDATA REG_SZ C:\Documents and Settings\&username%\Application Data

You can also find out what machine they are connecting from. The CLIENTNAME value will be the computername the user connected to the terminal server from.

CLIENTNAME REG_SZ Lazyadmin

If you are not working in a thin client enviroment, or need to convert SID to username you can also use SidToName. With this tool run the command: sidtoname SID - will resolve the username for the SID specified sidtoname SID computername - will resolve the username for the SID specified on the computer specified

For more information see:

SIDtoNAME Homepage