I have posted this question at the MacFixIt bulletin board (http://www.macfixit.com/ultimate/Forum8/HTML/000474.html
) but would like to have more suggestions.
In a nutshell, my 5400/180 (upgraded to 6.4Gb HD and 88Mb of RAM) was running happily for months on OS 8.6, but suddenly it just refused to start up, even from the OS 8.5 CD. After many days of repairs, reconfigurations and tests, the problem still persists. Since the last post at MacFixIt I tried to put back the old 2.4 Gb HD with OS 8.5 on it, but it still refuses to start up from the 8.5 CD, and then just refuses to start up from HD. This eliminates the likelihood of software and HD as culprits, but a few technicians suspect the RAM while I suspect the logic board. The latter already had a problem when I acquired the computer which disables the screen brightness setting but never caused any problem, but the RAM causing problems?
I am at my wit's end, so any suggestion would be very welcomed.