Another method for future reference: use the XP disc to use the recovery console to to repair/re-write your MBR. It would have wiped grub, and set XP back to being the 'only' OS seen at boot.
From there you can use EasyBCD to add an entry for Linux in the boot menu.
Mint should have also added an XP entry to the Grub Boot loader. If not, it could have been added manually and set as default. From there you could have done some jiggery-pokery to use the Win boot loader as the default loader.
As far as Linux/Windows boot shenanigans go - a lot of us have been there and swore at that. You're not the lone stranger