Hardware Reference
In-Depth Information
If your system uses Serial ATA (SATA) hard disks, keep in mind that the cable and con-
nectordesignusedbysomemotherboardsandSATAharddisksdoesnotincludealocking
mechanism. The cable might have become disconnected from the motherboard or hard
disk. SATA cables can also fail if they are bent or cut. Replace damaged cables and make
sure the cable is connected to the drive and motherboard or host adapter card.
The system won't boot up; it says
Missing operating system
Missing operating system
on the screen
When your system boots, it reads the first sector from the hard disk—called the
MBR—and runs the code contained in that sector. The MBR code then reads the partition
table (also contained in the MBR) to determine which partition is bootable and where it
starts. Then it loads the first sector of the bootable partition—called the
volume boot re-
cord
(VBR)—which contains the operating system-specific boot code. However, before
executingtheVBR,theMBRcheckstoensurethattheVBRendswiththesignaturebytes
55AAh
. The
Missing operating system
message is displayed by the MBR if it finds that
the first sector of the bootable partition (the VBR) does not end in
55AAh
.
Several things can cause this to occur, including the following:
•
The drive parameters entered in the BIOS Setup are incorrect or corrupted.
These are the parameters defining your drive that you entered in the BIOS Setup, and
they're stored in a CMOS RAM chip powered by a battery on your motherboard. In-
correct parameters cause the MBR program to translate differently and read the wrong
VBR sector, thus displaying the
Missing operating system
message. A dead CMOS
battery can also cause this because it loses or corrupts the stored drive translation and
transfer mode parameters. In fact, in my experience, a dead battery is one of the more
likelycauses.Torepairthis,checkandreplacetheCMOSbattery,runtheBIOSSetup,
gototheharddriveparameterscreen,andenterthecorrectdriveparameters.Notethat
most drive parameters should be set to auto or autodetect.
•
The drive is not yet partitioned and formatted on this system.
This is a normal
errorifyoutrytobootthesystemfromtheharddiskbeforetheOSinstallationiscom-
plete. Boot to an OS startup disk (floppy or CD) and run the SETUP program, which
will prompt you through the partitioning and formatting process during the OS install-
ation.
•
The MBR or partition tables are corrupt
—This can be caused by boot sector vir-
uses, among other things. To repair this, cold boot (power off, then on) from a Win-
dows XP or later install disc and use the FixMBR command in the Recovery Con-
sole(XP)orRecoveryEnvironment(Vistaorlater),whichrecopiestheMBRcodebut
doesn't alter the partition table. Then reboot. If the message persists and you need to
recover the data on the drive, you then must either rebuild the partition tables from
