Seatools doesn't support RAID.
If you haven't set up the RAID array yet, you can change the controller mode in the BIOS setup to IDE or AHCI. Seatools should now recognize your drives. When finished, change the BIOS back. You can't do this once the array has been set up and initialized, of course, but until then it won't cause a problem.
RB, I had read elsewhere that SeaTools has issues trying to detect drives through a RAID controller, so I did as you suggested. I removed my SSD (used as my Win 7 boot drive) first, then powered back on, entered the BIOS and set SATA drives back to "IDE". I then booted from the SeaTools for DOS CD and it did indeed find the Seagate HDD. Problem now is SeaTools won't run any of the tests on the drive, they start and then just hang. That's not a problem for this forum though.
Thanks for your help.