Making a bootable USB stick from a CD (not a Linux distro)

[Adam Funk]

I have a bootable CD of the Spinrite software, & I'm trying to make a
bootable USB stick from it.  I tried the following:

$ readom  dev=/dev/cdrom  f=spinrite.iso

$ file /opt/downloads/spinrite.iso
/opt/downloads/spinrite-6.0-boot.iso: ISO 9660 CD-ROM filesystem data 'SPINRITE_V6_BOOT' (bootable)

$ sudo dd if=spinrite.iso  of=/dev/sdb

I also tried the last command with the conv=notrunc option, & various
bs settings.  Every time, I end up with a USB stick that will mount
and contains the SPINRITE.EXE file, but when I try to boot a laptop
from it, I get an error to the effect that it's not bootable.

$ sudo parted -l
...
Error: /dev/sdb: unrecognised disk label
Model: TOSHIBA TransMemory (scsi)
Disk /dev/sdb: 31.0GB
Sector size (logical/physical): 512B/512B
Partition Table: unknown
Disk Flags:
...

Any idea what I'm doing wrong?

Thanks,
Adam