Welcome back to another free training video from IT Free Training. In this video I will
look at two different troubleshooting techniques that can be used with device drivers. The
first is last known configuration and the second is device driver roll back.
Last known configuration works by storing a working set of your configuration that you
can revert back to if your system fails to boot after a system change. The configuration
of your computer is stored in the registry under H Key Local Machine, System, CurrentControlSet.
When you install a device driver or make a configuration change the change is made in
the current control set. The problem is that the change may not take effect until you reboot
your computer. When the computer reboots, sometimes a change can cause the computer
to crash or freeze on boot. To allow you to recover from this and boot
your system, Windows does the following. When Windows starts up and the user successfully
logs into Windows, Windows assumes that the current configuration must be working. Windows
will then copy this configuration to a backup configuration set.
Let’s have a look what happens when a buggy device driver is installed that requires a
reboot and crashes the computer on start up. When the driver is installed the configuration
for that driver will be put into the current control set. When the computer is rebooted
the current control set contains the buggy driver and the computer will fail to boot.
When this occurs you want to revert back to the working backup control set. To do this,
during system boot up press F8 and select the option last known configuration.
This will boot the system using the backup configuration that was saved the last time
the computer was started and the user successfully logged in. Using the backup configuration
you can hopefully get your computer booting again without the buggy device driver crashing
the system. In some cases you may install a buggy device
driver but were able to reboot the computer and login. When this occurs, the backup control
set will also contain the buggy device driver and thus you can’t use the last known configuration
to undo the changes. Windows has a device driver roll back feature,
which is available assuming you can boot the computer and login. Using this feature you
can roll back a device driver, returning the system back to what was present before the
device driver was installed. This will be either the previous device driver or no device
driver in the system. I will now change to my Windows 7 computer to have a look at how
to use these two features. I will first demonstrate how last known good
configuration works. To do this, first of all open device manager from the start
menu. Notice in device manager that there is a missing device. I will install a device
driver by right clicking the device, selecting update device driver and then browsing to
the files for this device driver. Now that the device driver has been installed,
I will now reboot the computer. Sometimes when you install a device driver the computer
will blue screen when the computer starts up. If you can’t login into the computer
it makes it difficult to remove the problematic device driver.
Remember that last known good configuration does not copy the current configuration
until you login. Currently I have not logged in so the changes that I made when installing
the device driver have not been saved to last known good configuration. Why? Well, until
I login Windows will assume this configuration has not proven itself to be stable.
To demonstrate how to use last known configuration, I will simulate a driver problem by manually
causing a blue screen like this. If you are curious about how to do this, see the description
for this video for more information. The system will now reboot. After the bios
screen and just before Windows starts up press the F8 key. This will display the boot options.
It is easy to miss the timing of this so you have to be quick. There are a lot of troubleshooting
settings on this screen. The one that we are interested in is last known good configuration.
If I select this and let the computer boot up, Windows will use a configuration that
it knows was used previously to boot the computer and allowed the user to login.
To demonstrate this, once the computer has started up and I have logged back in I will
once again open device manager. Notice in device manager that the device driver that
I installed previously has been removed and no driver is currently installed. You can
see how last known good configuration can quickly recover the system from a recently
installed device driver that is causing your system to crash on boot and you can get back
to…… well the computer blue screened again so I guess some more troubleshooting is required.
Sometimes a buggy device driver is very difficult to troubleshoot. A buggy device driver may
cause a blue screen to occur very randomly and you may not know what is causing it. A
lot of the time upgrading to the latest device driver will fix these problems but sometimes
an earlier version of the device driver may prove to be more reliable.
Once the computer has rebooted and I have logged back in, I will once again open device
manager from the start menu. The last device driver I installed was the video driver. To
roll back the device driver to the previous version, right click the device driver and
select the properties for the device driver. On the driver tab, press the button roll back
driver and the current device driver will be removed and the old device driver reinstalled.
Once I confirm this is what I want to do and then close the properties for the device driver,
you will notice that the display adapter device driver has changed back to standard VGA graphics
adapter. In most cases upgrading a device driver to
a newer version will be more stable than keeping an older device driver. In the rare case the
newer device driver causes more problems, remember the rollback device driver option
will quickly remove the device driver and return you back to the previous device driver.
Unlike last known good configuration, this can be done at any time and is not affected
by how many times you login to the system. Well’s that it for the free Windows 7 course
from IT Free Training. If you have watched all the videos in this free course for Windows
7 I would like to thank you for taking the time to watch. All of our videos are free
on YouTube and only by you watching these videos can we keep doing what we are doing.
If you like this course, please feel free to look at our other free courses like Active
Directory and Application Infrastructure for Windows Server 2008 R2. For the last time
in this Windows 7 training course, thanks for watching.