646 Computer Service and Repair
the boot sector, and the file allocation table. This essentially erases any record
of the other partitions. The second situation affects some older computer BIOS
systems that cannot access large disk drives. A third-party tool called an overlay
program is used to remedy the large disk access problem. The
fdisk/mbr
command
can overwrite the information used by the overlay program to allow large disk
support. This can further complicate or compound the program.
Many third-party software systems can repair an MBR, especially if the
software is installed before the problem develops. The software recovery systems
make a copy of all vital information including creating a copy of the MBR.
When an error occurs, the recovery software can use the copy to help recover
the damaged system. In addition, third-party software systems can be used to
inspect, copy, and modify bytes in each sector of the hard drive. This is a very
powerful tool, but using it can be very time-consuming.
Additional Mechanical Problems
There are a number of other mechanical faults that cause problems in PCs.
Boards, cards, and cables can go bad, but these occurrences are not all that
common. You will find that, along with hard drive failure, most of your other
mechanical problems will arise from two areas: improper hardware upgrades
and accumulation of dust in the system.
Figure 15-4.
Examine your hard
drive through the
command prompt.
If you can see your
files, you should be
able to repair the
drive and save the
data.