NTFS is a better file system for Windows. You would be better off creating an NTFS partition for windows XP and a separate FAT32 partition. Windows would see the FAT32 partition and read/write to it (as drive D: or something like that). Linux can also read/write to the FAT32 partition, so you can share your misic files, etc. Linux will read NTFS data, but will cause major problems if you try to write to the NTFS partition. I recommend Acronis Partition Expert: http://www.acronis.com/products/partitionexpert/ You can create a bootable CD to use for partitioning.

Also, if you dual boot, remember that linux will be handling the booting through the linux loader (LILO) program. Make sure that you boot first to the drive that has Linux on it. Either move the 20 GB drive to IDE primary (hda), or set the BIOS to boot first from the IDE secondary drive. LILO can handle dual boot without any problems. I dual boot with WinXP and Linux(Knoppix) using a single drive.