written by: J. Edward Casteele•edited by: Tricia Goss•updated: 11/4/2010
Having a computer repeatedly shut down and reboot can be frustrating and potentially damage your computer. Learn how to diagnose the problem and fix it, regardless of whether it is being caused by hardware or software issues.
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Boot loops, the repeated unwanted rebooting of a computer, can happen because of either hardware or software problems. If the boot loop is not taken care of then not only will you be subject to the annoyance of unwanted reboots, but some of the core files of the operating system can be damaged. When you encounter boot loops on a Windows XP Home Edition computer, you will be able to fix the problem easily if it is software-related; Windows XP features a built-in repair function that can be used to perform a special type of installation known as a "repair install" to replace damaged files with uncorrupted copies.
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How a Repair Install Works
A repair install is performed by overwriting the operating system's core files with new copies directly from the Windows XP installation disk. Only the core operating system files will be overwritten; all of your Windows settings will remain the same, and any programs that you currently have installed on your computer will still be available once the repair install has finished. By overwriting damaged or corrupted files in your copy of Windows XP Home, the repair install will eliminate any potential software cause of your rebooting problem.
Because a repair install rewrites all of the core files of Windows XP, the repair process takes approximately the same amount of time as a standard installation of Windows XP Home. Since there is often no way to determine exactly which files have been damaged or corrupted to cause a boot loop, there is no way to selectively install core system files. They all must be overwritten to make sure that the damaged files are completely replaced.
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Ruling Out Hardware Problems
Before beginning a lengthy operating system repair process, take the time to make sure that the rebooting problem isn't being caused by your computer's hardware. The majority of hardware-related boot loops come as a result of overheating, a hardware problem that is generally quite easy to test for.
While the computer is running, look at its case fans and make sure that they are functioning properly. Use compressed air to clean any dust or debris that might be collected in the fans, and make sure that they are unobstructed so that air can flow properly into the case. You may also wish to shut down the computer and use air to clean the processor's heat sink and fan as well, to make sure that every fan in your case is dust and dirt free. If the fans are not operating correctly, replace them with new fans.
Open your case while it is running if you continue to have hardware problems. This will allow excess heat to vent from the case, and can also allow you to increase airflow by placing a small fan nearby that will blow directly into your computer case. If the boot loop continues after this it is safe to assume that it is not being caused by too much heat in your system.
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Performing a Repair Install
If you need to perform a repair install on your Windows XP Home computer, insert your Windows XP installation disk into the computer's CD or DVD drive and reboot the system. If you are prompted to boot from the CD, press the indicated key in order to do so; if you are not prompted, reboot the computer again and enter your system's BIOS setup to change the boot order so that your CD or DVD drive is booted before your hard drive.
Once you have entered the Windows XP Home installation program, follow the on-screen prompts to begin the installation of Windows XP. The installer will detect your previous installation and will give you the option to repair it instead of installing a new copy. Choose to repair the existing installation, then wait while the installer begins overwriting your existing install's system files.
You will need to re-enter some information such as your name and your Windows XP Home product key, and may have to reset your regional and network settings as well. When the repair install has completed, though, you will no longer have to worry about software problems causing your computer to repeatedly shut down and reboot itself.
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Other Possible Problems
If the computer still has problems with rebooting after making sure that it wasn't overheating and performing a repair install, the problem is most likely in the power supply or the processor.
If the problem is in the power supply then it is a result of the system requiring more power than the power supply is providing; the most common way of fixing this is to simply buy and install a new power supply that can supply more wattage to the computer. If the problem is with the processor then it is likely an early symptom of complete processor failure and should be treated by replacing the processor with another CPU that is compatible with your system's motherboard.