You didn't say what version of Word you are on. The latest Word is 2010. I'm running 2004 on my iMac and have no problem with it, except that it is under Rosetta. It sounds like you are on a PPC, so Rosetta isn't an issue.
In any case, Word is not attached to the OS, and of course is made by Apple's chief competitor, at least in the PC world. One does not control the other.