Have a look at the answer to question 1: BigAdmin: Xpert Session - Solaris 10 OS Installation (http://www.sun.com/bigadmin/xperts/sessions/17_sol10install/questions3.jsp#21)
They recommend external...
There no such thing like solaris key. You register at sun.com and pay for subscription to receive latest security patches and other patches for Solaris operating system. You get some id at sun.com...