The technically correct answer to the question about remapping partitions is yes, it can be done. And yes I have done it before and had it work. As you probably know, I don't use Windows, but I have done it on computers for other people.
The practical answer to the question is maybe. Let me explain. If you are talking about Windows ME on the 6th logical partition of the second drive, forget it. The only way you will boot that is with a size 12 combat boot! At least I have never been able to get it to boot.
If you are talking about getting two copies of XP, both on primary partitions and neither on the first partition, to boot then yes you can get both to boot. It requires some clever use of the hide and unhide commands and also the remapping command. I have done this also, but I admit that there was some trial and error involved. At least there was for me.
If you have one copy of XP on a primary partition, but not the first one, the remapping command will usually do the trick for you. This is not too difficult to accomplish. I have done this several times.
When it comes to logical partitions, that is a different story. I have never been able to do much with booting any Windows from a non-first logical partition. I have been told that it is possible, but I have never done it or seen it done with my own eyes.
I think if I were you I would pick muskratmx's brain about this. I believe he has had a lot more experience at booting Windows in strange places than I have. Another user here that I think has had a good bit of experience in this area is probably Chi. I go out of my way to avoid having to do stuff like that.
I don't have a computer around now that has Windows on it at all so I can't play with the various positions now. The boot stanzas I posted above, I did for memory but I think the form is correct, and should work with Windows XP on a non-first primary partition. If my memory is correct, which can't always be relied on anymore.
As far as the pointer analogy, Muskratmx is technically correct. The kernel is the part in the mbr. and with the stage 1.5 and stage 2 modules it does make a complete, though limited, operating system.
But, as I myself pointed out later in the thread, it is easier for me to think in terms of pointers. As long as you understand that it is a gross simplification for practical application use, I see no harm in the analogy.
If you will look at my post in the other thread about chainloading Linux you can see how that works. It is pretty simple once you get the hang of it. and it does have several advantages over the automatic installer's boot stanzas. Just because I used a separate master boot partition doesn't mean that it has to be done that way. You can use the Mint /boot as the master boot for the other installs if you prefer.
If I can help you understand something I will be happy to share what little I know with you.
I hope this was a little bit helpful.