How to Reinstall Windows XP Over Itself and the Consequences

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Reinstalling Windows XP over itself

The FAT32 and NTFS anomaly

It is possible to recover Windows XP just by reinstalling it over itself by running its setup program on its installation CD. None of the settings are lost, the files and folders remain intact, and you can use all of your programs and your Internet connection, etc. However, you will have to reinstall all of the updates that Automatic Updates installed. You can check this for yourself after you have reinstalled XP over itself by opening Add or Remove Programs in the Control Panel. You must have the Show updates option enabled.

To run the XP setup program all you have to do is boot from the XP installation CD. You must have the Product Key, because you have to enter it, and you may have to set the BIOS to make the CD/DVD drive the first boot device in order to be able to boot the system from the installation CD.

If necessary, read the BIOS pages on this site to find out how to access and use it.

However, keep reading if XP is installed on a partition formatted to use the NTFS file system and you have set up User accounts that are created to allow other users to have customised Windows setups with their own login passwords...

Reinstalling Windows XP over itself by booting from the CD will not remove the customised settings and data, but if the NTFS instead of the FAT32 file system is installed, it will create a new user account - even if you use the same user name as you did when XP was first installed.A new user account will not be created if XP is using FAT32. (XP's native file system is NTFS, but it will automatically use FAT32 if upgraded to from a Windows 98/Me system.) Because of this anomaly, if XP is using NTFS, after the reinstallation you won't be able to access the old user's My Documents and e-mail files, etc., since each user account is associated with a different Security Identifier (SID) - a unique 128-bit random number generated during the installation process.

Opening My Computer, right-clicking on the C: drive, and then clicking Properties brings up a window that tells you which file system that drive is configured to use.

To remedy this situation, you have to log on as the Administrator and change the file ownership. On a corporate network using XP, the network administrator would do this, but on a home-based system, not part of a domain, Windows XP Home and Professional versions do not have the Security tab from where the changes are put into effect. In that case, you will have to use the following method that works for both the Home and Pro versions:

Press the F8 key before the screen that says that Windows XP is loading appears to bring up the boot options. Often XP boots so quickly that you don't get the chance to press the F8 key. If so, the seemingly drastic step of turning off the computer during the boot process will force XP to bring up the boot-options screen on restarting the computer.

Choose the option to boot in Safe Mode. You will have to log on using the user name Administrator. You will also need to enter the password you created when Windows was first installed.

Once in Safe Mode, open Windows Explorer and scroll down to the Documents and Settings folder (of the C: drive). You should see two folders with your user name. The newer one will probably be distinguished in some way from the original. To see all of the folders, you may have to go to the Tools menu and click Folder Options => View, and then enable the option to Show hidden files and folders.

In the Documents and Settings folder, click View => Details to see the dates when each folder was created. Right-click the most recent folder with your user name on it, and click Properties. You should see a Security tab. Open it, and click Advanced. Click the Owner tab, and highlight your new user ID from the Change owner to list, and check the Change owner on sub-containers and objects box, and click OK. You should now be able to access your files.

Note well that although reinstalling Windows XP over itself does not remove the customised settings, folders, and files (you can still run your applications and use your Internet connection, etc.), you will have to reinstall all of the updates and security patches by visiting Microsoft Update. For example, if you used Windows XP SP2 CD, you will have to install all of the updates that were made available since SP2 itself was made available. Your computer will be vulnerable until the updates are installed, so install them as soon as possible.