A APM and GPT riddle

[sjs]

hi

My macbook's internal HD is partitioned as Apple Partition Map, yett boots up fine!

Two weeks ago i reinstalled from original DVD as per your suggestion and then used Migration Assistant ("from other computer attached to this Mac") to migrate user data from an attached GPT FW disk. All worked fine.

Today I need to repeat the process but can no longer install to the internal drive because its now APM. I presume the drive must have been GPT as of 2 weeks ago since it installed fine then. In fact, I think I had a similar problem then, and I had to reformat the drive GPT back then too.


1) Isnt this supposed to be impossbile to boot intel macbook from APM yet I am doing it?
2) How can it spontaneously change?

A real riddle!

ps - i am going to hold off repartitioning as GPT/restoring until i hear back from you in case you want to verify something on this disk