moving a disk

[PJ]

I am trying to move a 7.2 installation to another computer where it is
to be the only OS acting as a server for the lan.
On bootup I get the message:
Using drive 0, partition 3.
And there it hangs.
I have tried to rewrite the mbr but that did absolutely nothing.
fik ad0 returns:
partitions 1,2,3 are <UNUSED>
Parrtition 4 give the cylinder, heads, sectors, blocks stuff

The disk did boot up on another box...

What should I do? And what information do I need to supply or look for
to solve this.
I'd rathernot go through another installation even if this is farly
elementary.
Oh, yes... all my former problems were definitely software related as I
have checked and double, triple checked my HDDs and cannot find any
problems therewith.
TIA