There are two ways that programs can access hard disks, via LBA/Extended INT13 calls, and via the (very) old standard INT13 calls which use a cylinder/head/sector (CHS).
Programs that access the hard disk via CHS are required by the old DOS partitioning standards that partitions must begin and end on a cylinder boundary. XP obeys this restriction when creating partitions so that if you happen to use an old program from DOS it will work properly.
The last cylinder boundary on modern hard disks does not coincide with the last addressable sector (LBA) of the drive, so on any disk formatted with a format utility that obeys the cylinder boundary restriction, there will be a very small (8 MB or less) unformatted area.
You can get around this by using a formatting utility that formats without obeying the cylinder boundary restriction. (I believe Partition Magic may allow the end of the partition to end on a head boundary rather than a cylinder boundary, thus enabling the use of almost all of the extra space).
There is no longer any need for any formatting utility to obey this restriction, as even if you used a DOS program that uses the CHS method of access, it couldn't access the entire disk anyway (CHS can access a maximum disk size of only 8.4 GB - 1024 cylinders, 255 heads, 63 sectors per track, 512 bytes per sector).