The Seagate and Philips were both connected at boot, but not the WD -
but having now rebooted with the WD plugged in, it makes no difference.

Just for the record, I have no problem with flash cards or thumb drives
- apart from the fact that no matter what I do, I cannot make thumb
drives bootable (I know that it can be done as I have a Mandriva thumb
drive which boots just beautifully).

All these drives are formatted as ext3 - do you think it would make any
difference if I switched to another file system?