It's because you have done a parallel installation, you now have two Windows XP installation and you could still access the original installation by adding it to the Boot.ini file. These parallel installations were more common during the NT4 era and were mainly used for debuging and for troubleshouting a non-booting installation or for disaster recovery of personal files. Unless you can successfully repair the original installation via the parallel one and due to the nature of shared folders on Windows installations parallel installations tend to be problematic to maintain and are prone to problems, it is not recommended to use these installations in a productive environment or for your day to day usage. I strongly recommend that you backup your personal files and that you reinstall Windows again, this time opting to format the drive onto which Windows will be installed.
John