Any two GUIDs are very likely unique (not equal).
See this SO entry, and from Wikipedia
While each generated GUID is not
guaranteed to be unique, the total
number of unique keys (2^128 or
3.4×10^38) is so large that the probability of the same number being
generated twice is very small. For
example, consider the observable
universe, which contains about 5×10^22
stars; every star could then have
6.8×10^15 universally unique GUIDs.
So probably you have to wait for many more billion of years, and hope that you hit one before the universe as we know it comes to an end.
