can’t ‘boot cdrom’ to install Sol 2.7

420R previously loaded with Solaris 8 but I need to reload (and repartition) Sol 7 on it. At the OK prompt I get:

boot device /pci@1f,4000/scsi@3/disk@6,0:f File and args: -r
Boot: cannot open kernal/unix
Enter filename [kernal/unix]:

Disk 2 in the system had /usr on it which I formated last night, knowing it would become a mirror. Do I have to blow away Sol 2.8 first? Won’t Interactive Install do that during repartition prior to install? Anyone know the filename it’s looking for orhow to find it? Sorry, probably easy but I’m an ex-AIX admin still learning Solaris. Thanks!

Regards,
David