I just walked through an install of Oracle 10g 10.2.0.2 on Solaris 10 x86.
You will find a description here: <http://bikle.com/protected/o10gR2_solaris10x86>
Near the end of the writeup, you will notice that I had a question about the Solaris 10 projmod utility.
Is it possible the Oracle installer is looking for /etc/system? [ which is gone in Solaris 10 ]