Partitions and Mystery Data

When I first got my new mac I wanted to test out some games, so I went through boot camp to install XP and well I didn't read the instructions first (yes my fault) so I had it set to format the drive to FATS when in the instructions it wanted NTFS. Don't worry, it is all working after I restored the system to all mac then (finally) found the instructions and used boot camp again. But the second time I was looking at the partition section of boot camp and saw there was about 5 gigs of new data! hmm... thats odd! Any one els see this?? I know its only 5 gigs but Im planning on repartitioning the drive again and don't want to loose more space! allrighty, well thanks for your time!