When you reclaimed the unallocated space did you try to expand the Primary partition to use it? And if so did you change the drive’s format to exFAT cause FAT32 doesn’t support drives larger than 32MB.
The next consideration is does Windows XP support exFAT. If not you may be limited to using the slow NTFS format on it.
Another thing to remember, Windows doesn’t support secondary partitions on removable drives.
Have fun. 
