How are you attempting to boot from the cdrom? If not already doing so, try typing boot cdrom - install from the ok prompt. If the cdrom is attached and the OS cd is good, the system will boot and the installation program should start.
For the future......
If you have just installed the new disks to a solaris box, you can make sure that the system sees them by doing the following:
from the "ok" prompt:
setenv auto-boot?=false
reset
probe scsi all
at this point, the system should seach for and list all attached scsi devices, including your new disks
If you see your disks:
setenv auto-boot?=true
boot -r
Sorry for being repetitive if you have already tried all of this!!
HTH
Jason