weldon said:
Because of the 4gb limit in FAT32 volumes, you might be better off to just mount your NTFS volume in OS X and create the disc from there. OS X can read NTFS volumes just fine, it just can't write to them. So really, when you create the ISO file in XP, you only need to reboot into OS X and then burn a disc from the .iso on your XP partition.
Are you familiar with Parallels? There are no partitions, no limits. You set up a virtual machine and it creates a file which, when the VM is running, it reads and writes to as if a hard drive. You can set it to be a fixed size or dynamically resize as needed.
You also can set OS X folders to share with a VM. As MacRumorUser stated, you could simply follow the entire process for creating a slipstreamed disc, (ripping, replacing files etc), but stop at burning, instead creating a disc image, dragging to shared folder and burning in OS X.
Oh, and the maximum file size for FAT32 may be 4GiB but, even if it were a partition being used, XP SP2 fits on a single CD, so this wouldn't be a problem anyway.