Possibly off-topic question - I am a n00b

[Phil Hart]

Grub 2 works perfectly when booting from a USB memory stick on the 
machine on which it was prepared.

If I use the same USB memory stick on any other machine, I get "Entering 
rescue mode... \n error: no such disk".

On the machine on which the USB memory stick was prepared, the target OS 
is on the third internal physical disk (sdc), and the USB memory stick 
appears as "sdd". On all the other machines, there is only a single 
internal disk (sda).

What am I doing wrong?

(A bar of virtual chocolate is offered to anybody who even tries to help!)