Protocols/MSNP/MSNP13/MachineGUID
MachineGUID
The MachineGUID field of a Protocols/MSNP/Commands/UUX command is a unique GUID representing the computer. It is used for the Sharing Folders feature.
It's usually stored in the Windows registry here:
"HKEY_USERS\S-1-5-21-1960408961-688789844-682003330-1003\Software\Microsoft\MSNMessenger\MachineGuid"
Other OSes or MSN clients do generate their own MachineGuid. It is valid to generate your own MachineGuid as long as you continue using the same during your session.