A useless bit of geek trivia here, that may come up one day in a pub quiz, although it is pretty unlikely.  But just in case this question has kept you awake at night wondering there are 122 bits of random information in a GUID that makes for  2^122 or 5,316,911,983,139,663,491,615,228,241,121,400,000 possible combinations.

So the short answer is quite a lot.