You can boot any OpenBSD install image, and choose 's' to get to the shell
prompt and 'dhclient int0' or 'rtsol -F int0' (replace int0 with the real
network interface) to get network access, nab the script by typing:
ftp http://code.freedaemon.com/releases/secwipe/secwipe
and then type:
sh /secwipe /dev/rwd0c
to ewrase 'wd0' the first ide drive on the system. use '/dev/rwd1c' for the
2nd, '/dev/rsd0c' for the 1st scsi disk and/or a memory stick, etc. Be
very very careful, it really does destroy and ewrase all contents on the
drive, aka be sure you want to really wipe it for good.