Microsoft Office Setup DVD doesn't work?

I just bought Advent Laptop (Windows 7) and it already has Microsoft Word and other stuffs in there. I'm presuming they are trial versions. So, I had this Microsoft Office Setup DVD. It worked on other computers that I had but doesn't work in this new one. Is it because my laptop already has trial version installed? Will I have to uninstall those trial ones to get my DVD setup to work. I have used same product key for 2 laptops already.