|It doesn't matter what brand drive. Microsoft made a decision to not allow formatting a partition/drive larger than 32GB by using FAT32. |
The reason for that is that FAT32 used on large partitions produces large cluster size. That results in wasted space on the drive. In your case you need to do it anyway.
Download discwizard from the link below.
Your drive also has some backup software on it. That software may interfere with the formatting. You may need to use Disk Management in WinXP to delete the partition on the external drive and then use diskwizard to partition and format it FAT32.