Hi 'O' - You can't be right because I've had other drives showing in my Sys Prefs for years which aren't boot-up ones . . . and one of those missing, which I've mentioned above, is one of them. How, one could ask, can we make a drive a boot-up drive if it is never showing in our Sys Prefs . . . ?
Thanks for the response, anyway.
I attached a boot HDD (Lion Source) to my Leopard partition of my test MBP and got these results:
(Rasputin HD is a Snow Leopard volume on the test MBP)
Then I attached two data only HDDs and got these results:
Note that neither of them is displayed. To me the evidence is conclusive. Perhaps the prior OSs permitted displaying all HDDs.
I agree and accept. I'd never tried to use the second HD as a startup drive all the while it was installed. My MacPRo is still using Leopard but looking at the way you have explained, it surely has to be containing stuff for start-up before it can be seen as such so I must have unwittingly removed the relevant content from the drive that had been insitu for a long time and not installed such stuff in the other drive I've set up.
Have some points!