In my case I had several issues:
1) I needed to get a cable, since there was none in the A1200.
At the time I expected a really short cable, and the line-up
of the holes looked wrong, so I taped it.
2) Once I got the cable, the holes where in the right place
with respect to the cable length, but the RAM metal cover
was in the way - so I removed it.
I could screw the 40Gb 2.5i HD into place. :roll:
3) Trying to partition the 8Gb the OS sees into two 4Gb partitions appeared to work (including formatting), but
it couldn't recognize the partitions afterwards. :-?
From another Forum entry I found out it was a validation
issue: not enough RAM (only the 2Gb Chip RAM until my
Elbox 4Mb FastRAM arrives). :idea:
So I partitioned the first two partitions: 150Mb for
Workbench and 250Mb for Data - the rest will wait until
I need the space

I also have the 64bit IDE Controller package from Elbox
on order -> should give me the entire 40Gb (but how many
partitions is that ? :-D )
Now it boots really, really fast - and noiseless as well.
Next project: rebuilding the power supply for more Wattage.