Yes, you can boot linux using boot.ini.
You have to create an image of the linux kernel, namely, vmlinuz, and then you have to store it in a floppy. Then you have to store it in your C: and add the path to boot.ini.
BUT, the exact procedure is not known to me, but I have seen it in RedHat's site somewhere. Search there, and you will get the exact steps.
But, I advise you to consider lilo or grub, and this is my grub.conf file
title LINUX (2.4.20-8)
kernel /boot/vmlinuz-2.4.20-8 ro root=LABEL=/
and it boots into XP wonderfully.