Here is information on why XP is reporting the drive as less than what you
are expecting.
Several factors may come into play when you see the reported capacity of a
disk drive. Unfortunately, there are two different number systems which are
used to express units of storage capacity:
1) binary, which defines a kilobyte as equal to 1024 bytes, and
2) decimal, which defines a kilobyte as equal to 1000 bytes. The storage
industry standard is to display drive capacity in decimal format. Even
though in binary you have more bytes, the binary representation of a GB
demonstrates greater capacity.
Name Binary Decimal
Kilobyte = KB 1,024 1,000
Megabyte = MB 1,048,576 1,000,000
Gigabyte = GB 1,073,741,824 1,000,000,000
To verify that your drive is being seen in its full capacity, go into My
Computer, right click on the drive, go to properties and view the number of
bytes. As an example:
Capacity: 40,006,123,520 bytes 37.2 GB
In this example - the capacity is 40GB drive using decimal mathematics
(dividing the number of bytes by 1,000,000,000). However, using binary
mathematics, the capacity is 37.2 GB.