Creating a OpenBSD 3.5 bootable CDI create the following directory structure /OpenBSD /3.5 /Changelogs /i386 /tools /OpenSSH /patchesnow you should mirror the files from ftp://ftp.openbsd.org/pub/OpenBSD/3.5/i386/ into the directory 3.5(see above)  run in above the OpenBSD directory the following command above the OpenBSD directory mkisofs -l -L -v -r -T -V "OpenBSD-3.5" -A "OpenBSD v3.5-Release, Custom ISO, 01-05-2004, Please support OpenBSD http://www.openbsd.org/orders.html" -b 3.5/i386/cdrom35.fs -c boot.catalog -o openbsd-3.5.i386.iso -x openbsd-3.5.i386.iso ./OpenBSD/now you can burn the ISO image