@Avra,
Hey, thanks, I will certainly follow up your link. Having said that, a bit of a rethink to get round the issue:
For what I want, I can probably generate a GUID or simply use the Dropbox ID which is provided and is unique and get a similar effect:) The only problem may be that the server side code (for which I cannot control (at the moment) requires two additional fields (the machine name - I can fudge that with any old name) and the CPUSerial. If it is expecting a CPU Serial in a particular format and within certain bounds (ie. something like 56660000000 to 999923333000) then I'd need to make sure it's of that form. AND if it is checking for uniqueness (I don't know why, but it might), I'd need to generate a random number within the bounds.
Regardless, thanks for your response, I am sure I can use the details elsewhere even if I don't need it here and now.
And thanks to those others that have responded.
Kevin