310 and Mac - many thanks for the amazingly prompt responses.
310 - I take your point but the termination should be OK as it hasn't been changed since the drive worked initially - will check it again anyway. Have tried three different cables on the IDEs and all give the same result. I can't get my head around the mouse not operating either.
Mac - I understand about the drive size limit. but that shouldn't have been affected with the initial W95 setup. There appears to be something wrong with the MBR which won't allow access to the drives with FDISK (or the low level format utility). Given the variations in the hardware being tried, I am stumped as to any sort of failure common denominator - 2 Mobos, 5 H/Ds, 2 SCSI hosts and utility programs, different I/O options - where is the commonality?
There's something I'm missing (apart from a brain!) and, while the end product isn't an essential, I'd quite like to satisfy myself as to WTHIH!!
The club hammer route is looking more and more attractive.
Again, many thanks chaps
PS - I'm doing a few days of 'proper work' so won't be able to try much experimentation until after the w/e = will report back after that.