Flutterby™! :

Like me, y'all were probably hoping to put off knowing anything about this Pentium III serial number business 'til the smoke blew over. Well, it looks like that's not going to happen, and I've had to look at what's true and what isn't, so a few notes. First, here's Intel's document on how to use CPUID to access the PIII serial number (PDF). A few notes:

• The serial number protection scheme has been totally discredited, software which wants to read your serial number will.
• I can't find any references to anyone who's figured a way to change the serial number, that seems to be really burned in at manufacture time.
• The serial number also exists in a few PII laptop processors.

I started out a skeptic but I'm now willing to believe that it might be handy for some copy protection uses, scanning for the CPUID instruction isn't as easy as trapping code looking for MAC addresses or similar semi-unique machine identifiers, and what the CPUID is doing can be obfuscated with a little work.