Several possibilities:
1. If the disk format is FAT32 and if it was made by XP, then 32Gig is all
you can get, per partition. If NTFS, XP will format as large as you like
per partition.
2. BIOS/motherboard limit? Some older PCs had a limit at 32 Gig. If you
have one of those, then you are stuck with 32 Gig per hard drive as long as
you connect ot the disk controller on the motherboard. A solution would be
to install a PCI-to-ATA controller card, which has its own BIOS.
3. In theory jumpers could be used to limit a disk to less than its full
potential. Carefully read the disk documentation and remove any such
jumpers.
4. When you say "XP sees only 32 Gig" are you talking about Windows
Explorer or the XP disk mangement console? Explorer can only see formatted
partitions, and then only FAT32 and NTFS. The disk managment console can
see more, including unformatted space and non-windows partitions. It can
also delete partitions and create new ones. If you see a lot of free space,
try creating a partition in it.