HDD/RAID/NTFS/Windows XP

I am not sure what causes this:

I am running a RAID 0 on 2 40GIG hardrives formatted to NTFS Windows XP

When I check Partition Magic I see:

Local Disk[C:] NTFS 78,403.1MB Active Primary
[*] Unallocated 7.8MB Active Primary

What is the Unallocated space?

My guess would be random disk stuff like the boot sector, partition format data, ect. Though I've never actually known for sure.

JigPu

im guessing xp is like 2000 and reserves enough to convert discs to dynamic discs.