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Problems Installing Windows XP SP2
By Peter Lancett, eHow Contributor

Service pack 2 for Windows XP contained essential security updates and other additions.
Service Pack 2, or SP2, for the Windows XP operating system, or OS, contains software patches and updates, many of which are designed to tighten security and protect the OS when a computer is connected to a network, especially the Internet. It also contains additional software drivers, extending the number of hardware devices that the OS will support without the addition of extra software. The complex nature of the SP2 package of updates means that the SP2 installation routines sometimes conflict with software and configuration changes on some computers. 

Windows XP SP2 Installation Tips on Installing Windows XP SP2

Access Denied
The installation of SP2 requires the installation programs to have unlimited access to the OS system registry. The registry is a database of system processes and hardware program instructions and contains information on how services, program processes and hardware drivers should run. To update the registry, the SP2 installation programs need to delete certain keys from the registry which will not be needed following the installation. Other registry keys need to be updated. If you get an "Access Denied" message during the installation of SP2, a log file called "Svcpack.log" is created in the "Windows" folder, and this will list all references to registry keys that cannot be accessed. You can edit these registry keys by using a utility called "Regedit," but you should be aware that making incorrect changes to the registry can render the OS unusable. A simpler method is to restore the registry to default settings before installing SP2, because SP2 has been designed to work with an OS having default security access permissions.

There is no specific utility for returning registry settings back to their defaults, but you can perform a System Restore, using the System Restore Utility found in Windows Help and Support. Use the System Restore calendar to restore the OS registry to the oldest restore point, which will be a date soon after the OS was installed. This will remove any programs you had installed after that date, and these will have to be re-installed, but all your user settings, such as desktop preferences, plus any data files you have created and saved, will remain intact.

Adware Problems
Adware is software that is designed to automatically download advertising material to a computer. It is a background process, which means that it runs without announcing to anyone using the computer that it is running. Once it has downloaded advertising content, adware is responsible for making sure that the downloaded advertising is displayed on the computer. Service Pack 2 contains security updates that might prevent some adware programs from downloading and running advertising content, and some adware programs contain settings that prevent SP2 from installing. You should always remove all adware from a computer before installing SP2. This can be difficult, because adware is not always easy to find once it is installed on your computer. You can purchase and download many computer cleaning programs, which will scan your computer and delete any adware programs found.

Files In Use
Sometimes during installation of SP2, the installation fails because the installation programs find that files that they need to access are already in use. This can happen when programs you have installed are already configured to use these files automatically. An easy way to overcome this problem is to restart the computer in "Safe Mode." Safe mode is a startup option that you can select before windows has loaded, during the startup routine. Reboot your computer, and hold down, or continually press the F8 key on the top row of your keyboard. You will eventually see an option screen, allowing you to boot in safe mode. Safe mode only runs OS processes and services that are essential for the computer to work. It does not load other programs, so once you have started your computer in safe mode, you can install SP2, because no programs will be using the files that the SP2 installation programs need. Once SP2 is installed, you can restart your computer normally again. 

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