Hi Ric
Well I don't know what I did differently, but it's fixed!
Hoorah!
Yippee!
Woohoo!
....phew!
I don't know if it was anything to do with having reset the PMU and logic board etc, but I held the 'alt' key at chime as normal, and the OSX disc appeared, as it had before. I clicked on it, and it moved forward to a next page, which hadn't happened before. In the absense of anything else to try, I let it progress, and agreed to install OSX. Well, it couldn't make it any worse....!
I had an inkling that if I could get OSX up and running then I would be able to reselect the old 9.2 start-up disc, restart and go back to my old and comfy ways. Was a bit of a risk, but it worked on the second attempt (hung on one of the instal windows first time round). OSX installed, had a bit of a play in there to see what it was like (lookey lookey nice!) and then went back to OS9.2 start-up disc, held my breath, crossed my fingers and it worked!
So maybe unorthodox, maybe a fluke but I'm back where I wanted to be, 48 hours later and after an ENORMOUS amount of help and support from you.
I do need ot put some consideration to the best way to upgrade to OSX properly (presume ignore that corrupt portion of the start-up disc, and overwrite existing 9.2 OS with new OSX? but will come back and ask you first!!), which I plan to do in the next few weeks having bought all the new application software etc, but for now I'm going to write a shopping list including new RAM, extra memory and a 9.2.2 install disc!
Seriously, thank you so very much indeed for all your help Ric, you truly have been a real star. If there is some rating system to this forum please let me know and I'll gladly say my piece! You really have helped me immensely, and protected my sanity which is just as important I think!
Very very best wishes
Lucy
(x...!)