A built in, intentional limitation of Windows XP is that it will only create FAT32 (the older file system seen in Windows 9X\ME operating systems) partitions up to 32GB in size. If you have a disk larger than that and you wish to format it with FAT32, your only choice is to create multiple partitions of 32GB or less. There is an option however. You can use a boot disk from an older version of Windows such as Windows 98 or ME to partition the drive into one large FAT32 partition. Windows XP will then be able to use the space.
You can obtain the necessary boot disk files from here
Download the ME or 98 disk image, then use the FDISK utility to partition the drive and the FORMAT utility to format it with FAT32.