Same problem here on a 3 year old i386.I copied the iso file from the install CD ( /4.2/i386/cd42.iso ) and burned it to another CD.
This booted fine, and then I copied all of the OpenBSD file sets from the install CD to complete the setup.
When the CD that I burned booted up, I got a message at boot: "/etc/boot.conf too large"
I will submit a bug report tomorrow. I have ordered another install CD from the supplier.
