There are times when Windows XP becomes so corrupted it won't run correctly or won’t start at all and it seems that the only solution is to format and reinstall losing all data and programs.
In previous versions of Windows, correcting an operating system error usually meant formatting and reinstalling, resulting in loss of all your data. Windows XP repair feature won't delete your data, installed programs, personal information, or settings. It just repairs the operating system.
The system repair function will remove any updates you have previously installed that are not included on the CD. When finished, you may have to download all of the updates from Microsoft Windows Update, because they are all replaced during repair. It may be necessary to reactivate your Windows XP as well.