quick grub question

making progress on the mac pro installation front. have successfully gotten a triple-boot osx/ubuntu/xp setup to load and run on the mac pro. one thing that was necessary to the process was being able to pause the install process at both the partitioning and grub install steps. this was necessary in order to back up the windows mbr and restore it. the linux partitioning apparently corrupts the windows mbr necessitating the backup and restore during the overall install process. it is also necessary to be able to put grub elsewhere than the mbr, the suggestion, which worked for me, being to put it in the linux partition. made sense to me. but i read someplace here about grub not asking where it should be installed. is this, in fact, the case? or has this been changed/fixed? it would pretty much make the install impossible for me. if i continue to make progress i'll post back with a how-to. it's a bit arcane. thanks, BabaG