Microsoft office 2010 wont pick 2003

Hello,
I recently purchased and dowloaded office 2010 . my professor posted a syllabus online which uses microsoft word 2003, and now when i try to open this doc on my comp word 2010 says the file is corrupt and will not open. when i try to repair the file it still doesnt work.

on the other hand i can easily access my professors syllabus on another comp that uses word 2003

whats going on???
do i need i file converter? if so which one?