Every Linux partition you want to boot must have LILO installed to it. Additionally you can edit your lilo.conf and tell it which parittion to install to. GAG (just like any boot manager) will simply point to the partition you want to boot but if your family prefers the XP bootloader then no GAG won't work for you.

So here's what happens in chain booting: You boot your boot manager (whichever one you use) - you get a selection menu, when you choose to boot "OS Whatever" you're really just pointing to a bootable partition which also has a boot loader in it. So you activate the boot loader in that partition which then proceeds to boot your OS. Effectually you use a boot loader twice when you multi-boot.

BTW- GAG doesn't need its own partition, it installs in the outer edge of the disk just like any other boot manager including ntloader but GAG gives you a nice looking menu, nicer than LILO nicer than NTLDR fer sure!

Does XP have a new bootloader or is MS still using NTLDR? IF you absolutely MUST have the XP bootloader then install LILO to your Linux partition and edit the XP boot loader to point to it. How? - Sorry but I have no idea. I too have family that has yet to give up windows but fortunately they don't do it on my machine!