Bad signature on partition table

[john gennard <joney@clara.co.uk>]

I'm trying to upgrade,have started with my first
physical IDE Hard Drive and run into a problem.

hda was the original and a small disk, with a W95
installation, a small e2fs /boot partition and
FreeBSD from an earlier experiment. When I became
committed to Debian, I bought a second larger disk
and as hdb used it for Slink and later Potato.

Now I have a 20G drive to replace the small one, 
and eventually make room for Woody etc. I also 
intended to upgrade the CPU and M/Board next week.
I've had to agree to keep a 500Mb partition for W95,
so did the following:-

a. Removed hda3 (the boot partition) from /etc/fstab,
   and booted from a floppy to prove I would have no
   problem with Potato.

b. Physically changed the disks and installed MS-DOS
   6.22 onto the new one. I've never liked the fdisk
   with DOS/Win, so I booted into Potato to finish
   partitioning the disk as I had planned.

c. cfdisk hda gives the error message 'Fatal Error:
   Bad Signature on partition table - press any key 
   etc. to leave'
   fdisk hda gives no message - just locks Potato
   completely. If I try to re-login (as opposed to
   reboot), the message 'hda: lost interrupt' keeps
   recurring.

If I go into DOS and run format or fdisk to wipe
the disk clean, I continue to get the same messages
(I did this thinking the problem had something to do
with the first cylinder difficulty which I've never
understood - can't tell if it could as I don't know
what cyls fdisk has used for DOS). 
 
Can anyone please shed any light on my problem. 
A little OT; can two separate Potato installations
exist on the same box - if so I could put another
on the new disk - never have any great problem in
installing Debian, so that might clear things (at
least I could 'see' what I do partitioning.

Regards,                      John.