One of Vista problem is Dual Booting sometimes  little tricky to remove because of the new bootloader. Good news, I have trick to make it  disappear! As my other collection of powerful tricks.
Playing with dual-boot systems has killed many people’s hard drives, its so badly!. I would suggest massive back-ups before you try to remove part of a dual-boot system. If you mess up, you might be unable to boot to any of your partitions. You do this at your own risk.

These are useful steps you need to do:

1. Backup [very important]
2. Reboot and Boot to your XP CD-ROM
3. Start the Recovery Console
4. Run Fixboot
5. Run fixmbr to reset the master boot record
6. Exit the Recovery Console
7. Reboot
8. To remove the extra entry, edit the boot.ini file to remove the “Microsoft Windows Longhorn” entry.
9. Format Your Vista Partition

Interesting to rip music to mp3 files for free in vista?