Proliant 2500 not booting from SmartStart 5.50 CD

This is a thread I originally posted around two years ago, that time I
found a workaround, this time I can't figure it out.

I have a Proliant 2500 Dual PPro 200, 384Mb, 221 disk controller. The
machine will happily boot from CD and run Knoppix, I can run hardware
tests from UBD3.3 but it stubbornly refuses to boot from a SmartStart
5.50 disk, I just get an 'Invalid System Disk' error.

I've re-downloaded the ISO image and burned it on two different CD
writers but it is refusing to boot from either copy. It does have the
system utilities on the array but when you try to run ACU it prompts
me for the Array Conifugration Utility floppy disks unfortunately I'm
a floppy free zone these days!

Switching the CD-ROM from cable select to master fixed this problem
before but this time it makes no difference, it's almost like the
machine is trying to spite me!

Help!
J.