GRUB/LILO can load XP fine so there isn't much reason to use gag, but I don't think it will make much difference.
this forum for threads on partitoning. You'll find lots of useful stuff.
Make a FAT32 partiton, Linux can't write to NTFS well.
The bootloaders rely on the bios, so if the bios supports the keyboard, so should LILO/GRUB.