Possible Duplicate:
Is there any difference between a GUID and a UUID?
Whats the difference between a GUID and a UUID, and which should I use for true uniqueness?
Update: What things do I need for uniqueness too in the algorithm I choose?
1) MAC address of network card
2) 128 bits (isn't 64 bits enough?)
3) What if I have a multicore machine on the same MAC address. Isn't there a chance of duplicates?
GUIDs are 128-bit UUIDs. You can use GUIDs and be sure of their uniqueness.
A GUID is Microsofts implementation of a unique identifier (UUID).
A UUID is defined as
"Universally Unique Identifier (UUID) is an identifier standard used in software construction, standardized by the Open Software Foundation (OSF) as part of the Distributed Computing Environment (DCE)."
From Wikipedia.
If you need to create a new guid/uuid use my website:)