If your 48-bit LBA hard drive is attached to the system using a PCI ATA controller card such as one from Promise Technology, you need to make sure the controller fully supports 48-bit LBA. If the controller was provided with the 48-bit LBA hard drive when you purchased the drive, the controller should support 48-bit LBA. Most PCI ATA controllers have firmware or BIOS which must support 48-bit LBA. There's also Windows operating system drivers for the controller which must support 48-bit LBA. If you are having problems recognizing the full capacity of the hard drive, check the controller manufacturers web site for updated BIOS and Windows drivers.