new owner laptop has control over my calender in WLM

Hi, I recently sols my laptop and uninstalled every program exept Windows 8 of course. I am a user of Windows live Mail and the Calendat synchronises with the calendat on my smartphone. The new owner reinstaaked Windows Live Mail with a differrent account of course but he has full control over my calendar! He was so frinendly to warn me. We tested it. If he deletes one of my appointments they are deleted on my computer and smartphone. We tried an uninstaal with a proffesional uninstall tool (that also scans and deletes hidden files). We reinstalled Windows Live Mail from Windows Essentials but the problem remains. If he would delete my appointments, that would be a disaster for my business. How can we solve this problem? Philippe