So it's the actual compaq bios/RAID board telling you that no drives can be found?
I'm assuming that the SCSI drives are connected to the compaq RAID card here? It sounds like you need a compaq smartstart disc - it's a bootable thing with RAID configuration utilites and what not. The cards can sometimes complain if the hard drive geometry is changed. The usual sequence of events is to check the RAID card(s) for a vaid setup and boot record then to scan through the onboard SCSI buses.
If you have onboard SCSI then you can always put the drives onto the mobo's integrated SCSI and just use them as normal hard drives. That's what I'm doing at the moment on my proliant 1850R - it has a smartarray 221 controller that's currently unconfigured. I just moved the cable from the hot-swap backplane from the RAID card to one of the mobo sockets.
Mandrake 10.1 installed fine on the disks connected to the mobo, and the RAID card was detected too and showed up under /dev.
I don't know of any specific websites, but compaqlinux looks like it might be of help:
http://www.cpqlinux.com/
Hope this helps!