Some versions of Microsoft Office came with Frontpage and there was also a stand alone version of Front Page. Sounds to me like what you have is one which came with the Office program since the error is requesting Microsoft Office. This is what happens when you try to use pirated copies of programs. Plus remember also not all versions of Office contained Frontpage either. So it would have to be a version of Office which also had Frontpage included.

Ok, I'll ask my teacher, but if he says I somehow can't (public school :S) do I have to install Microsoft Office?
Have no idea what you mean by public school...if you are taking a class then the material should be provided. Were you told to install Frontpage on your personal computer or was this your idea?