When attempting to run Windows Update a message appears saying ‘Files required to use Microsoft updates are no longer registered or installed on your computer’. Clicking the ‘Install Now’ button to install the necessary files just causes the same message to appear again - it is almost like an endless loop! In the past I have been able to download updates alright, so this just seems like a recent phenomenon. The computer is running Windows XP.

Windows Update can be a somewhat temperamental service, and I have also found occasions when it does not wish to work properly and an endless loop situation arises. The first solution you can try is re-registering the Windows Update files, which are required for Windows Update to function properly. This is the most common solution to this error message, and most users report this will resolve the issue. Go to the ‘Start’ menu > ‘Run’ and type the following command:
regsvr32 wuapi.dll
and click OK. A message should appear saying ‘DllRegisterServer in wuapi.dll succeeded’. Click OK to close the message. We now need to register some more files, so repeat the above procedure for the following commands:

• regsvr32 wups.dll
• regsvr32 wuaueng.dll
• regsvr32 wucltui.dll
• regsvr32 atl.dll
• regsvr32 msxml3.dll

After all the above commands have been executed, try running Windows Update again to see whether the problem persists. Should the problem continue, there could be many different reasons for this error occurring, which unfortunately are too difficult and detailed for proper explanation. Therefore, in this situation a better option may be to complete a repair installation of Windows XP.

In theory, a repair installation should not cause any data loss, but will instead just replace the Windows system files with fresh copies. However, I strongly recommend you backup all important data before undertaking this procedure since there is always a risk things could go wrong, resulting in your data being lost. Once you have backed-up all your important data, find your Windows XP CD and insert the CD into the CD-ROM drive. Restart the computer and the computer should boot from the Windows XP CD (if not, you may need to re-configure the boot order of devices in the BIOS so the CD drive is checked for a bootable source before the hard drive). Please note, a message may appear saying press any key to boot from the CD - in this case you will need to press a key on the keyboard to trigger booting from the CD. Once the Windows XP Setup has loaded, you will be presented with three options at the main menu. Press ENTER to start the Windows XP setup. DO NOT press R to load the Recovery Console, as this is something different and unrelated to a repair installation of Windows XP. Next, the Windows XP licence agreement will appear, so at this screen press the nominated key to accept the licence agreement. A list of Windows XP installations will appear on screen. Since you only have one installation, there should only be one listed. Select the Windows XP installation and press the R key to indicate you wish to repair the installation (be aware, in the unlikely event that the R option is not available, this means you cannot repair the installation - in this case abort and end the setup and then please contact me again for further advice). Assuming the Repair installation is an option, after pressing the R key the repair installation should commence. During this procedure the computer will reboot and you may notice during the reboot, a message appears saying press any key to boot from the CD. DO NOT press any key, as you do not wish to boot from the CD during the repair process - just let the computer boot normally. At the end of the repair process all your data should still be intact, but you should check just in case. Then, try to access Windows Update and hopefully this should work correctly.