IS this because it was made for XP and I'm running Vista?
Yep.
Will docks designed for tabs not display right if you only have the light version of Object Dock?
If by light you mean free version, then I assume you are trying to use a dock designed to be tabbed as a standard dock, if so then no it will not look right as the settings in the .ini file are set to leave room for the tabs, so as a standard dock icons will be further away from one side than the other.