640 Computer Service and Repair
operating system to the boot strap program, you will see a progress bar appear
on the screen. When you see the progress bar, you know that the second stage
has begun and the operating system has successfully loaded the system kernel.
The operating system then initializes the hardware devices.
Failure during the second stage is usually the result of a corrupt required
operating system file such as
ntldr
or failure to properly detect and initialize a
piece of hardware such as the sound card. It can also be the failure of a required
hardware driver file.
The fastest way to repair a system failure that occurs during the loading and
initialization of the operating system is by reinstalling required system files.
Simply insert the installation CD/DVD and then reboot the computer. When the
installation CD/DVD boots, follow the screen prompts. For more information on
problems caused by hard drive failure that can occur during the second stage, see
the Hard Drive Failures section. Detailed troubleshooting methods for this stage
are covered in the Recovering from a System Startup Failure section.
Third Stage
System logon is the end of the second stage. Keep in mind that not all
operating systems require a logon. The third stage is when the desktop first
appears. During the third stage, startup programs, services, and applications are
loaded. The most common problems that can occur during this time are usually
due to corrupt or incompatible drivers and files.
File corruption
Files can become corrupt in various ways such as by virus attacks and
hardware failures. For example, an intermittent RAM failure can corrupt files
also if the file contents is being transferred or copied during the time of RAM
failure. Files are also corrupted by being stored in an area of the hard drive that
has a bad sector. All data saved to the bad sector is lost, thus corrupting the
contents of the complete file.
Overwritten DLL file
Certain files such as DLL can cause a system failure when inappropriately
applied in a software program or when they become corrupt. A Microsoft
Dynamic Link Library (DLL) file is an executable file that can be called and run
by Microsoft software applications or by third-party software programs. Rather
than write code from scratch each time a new software application is written, a
programmer can simply call a DLL from within the program they have written
and run the function they need automatically. One DLL can be used by more
than one software program at the same time. By reusing the same code contained
in the DLL, a programmer saves time and the computer uses less memory and
disk space. The term dynamic is used because the file can be loaded, run, and then
unloaded from computer memory when no longer needed.
One of the major software problems in the past is when a user loads a
software application from a disc that contains the necessary DLL files required
to run their software application. All too often, the DLL file on the software
disc overwrites the existing DLL already residing on the computer. If an older
DLL file overwrites a newer DLL file, an error can occur when the user starts
an application other than the one just loaded. A classic example is when a user
loads an older version of a software game on a computer that has other games
Microsoft Dynamic
Link Library (DLL)
an executable file
that can be called
and run by Microsoft
software applications
or by third-party
software programs.