Do not read this is you have any kind of attention disorder. 

Legacy Hard DRIVE issues still present.

These links are for reference. A Google search will find more like them. The subject cam cause confusion and get to be really much too deep. Any attempt to simply the issue is doomed.

Up untill about 1996 Personal Computers and Hard Drives Drives had issues moving from the CHS to the now standared LBA lauout. After that year it got a better. But it is still a problem. Sometimes.

 LBA
http://en.wikipedia.org/wiki/Logical_block_addressing
Quote

Until the release of ATA-2 standard in 1996, there were a handful of large hard drives which did not support LBA addressing, so only Large or Normal methods could be used. However using the Large method also introduced portability problems, as different BIOSes often used different and incompatible translation methods, and hard drives partitioned on a computer with BIOS from a particular vendor often could not be read on a computer with a different make of BIOS.

Cylinder-head-sector, also known as CHS, was an early method for giving addresses to each physical block of data on a hard disk drive. In the case of floppy drives, for which the same exact diskette medium can be truly low-level formatted to different capacities, this is still true.

Sector indices have always begun with a 1, not a zero, and due to an early error in MS-DOS, the heads are generally limited to 255[citation needed] instead of 256. Both the partition length and partition start address are sector values stored as 32-bit quantities.

In computer hardware, GUID Partition Table (GPT) is a standard for the layout of the partition table on a physical hard disk. Although it forms a part of the Extensible Firmware Interface (EFI) standard (Intel's proposed replacement for the PC BIOS), it is also used on some BIOS systems because of the limitations of MBR partition tables,