Installing on a recently acquired SS20

Looking at the SS20 successes in the list this is probably finger 
trouble with me, but here goes:

I have an SS20, dual 390Z55 processors with 352MB memory and a Turbo GX 
card and fitted with 2 * SUN branded 2.1GB discs.

Boots to the open boot prompt type boot cdrom
SILO appears and the instal kicks off ok on V0.42 and V1.0
Select Text install goes ok until we get to the partitioning bit.
On both 0.42 and 1.0 auto partition fails saying it cannot create 
primary partitions.
On both if I go into FDISK and manually remove the whole disk partition 
and create
new partitions it fails saying the disk partitioning is unreadable and 
puts me back to the initial
partitioning screen again.
If I leave the whole disk partition intact I get the same errors messages.

It almost looks as if the disks are write protected but I cant see how.

Any advice, abuse for stupidity constructive criticism will be 
gratefully received

Regards
Keith