Manufacturers of drives are driven by their marketing departments who report drive sizes in Base 10 figures to make them seem bigger. I.e., 250 GB = 250,000,000,000 bytes. In reality storage and memory space within a computer must be calculated in terms of Base 2 math and that's what WinXP reports to its users:
1 KB = 1024 bytes
1 MB = 1024^2 = 1,048,576 bytes
1 GB = 1024^3 = 1,073,741,824 bytes
Thus, one must make the conversion from Base 10 to Base 2 to get the true amount of space available. For a "250" GB drive, the actual amount of space = 250,000,000,000/1,073,741,824 bytes or 232.8306437 GB. That's the figure that Win/DOS should be reporting to you.
BTW, all these calculations were conducted on an old Intel 486 chip, so they could be wrong.
