How do I check what I own? I have Battle Isle 1, 2 and 3 purchased separately in the past, but how do I know if I have all the related content that they describe is present in the Platinum version. E.g. is History Storyline 1914-18 included with my version?

I own original box copy of Platinum. So. Can tell you that pack has same things. BI1 and it's two scenery CD's, History Storyline 1914-18, BI2 and it's scenery CD, BI3, Incubation and his add-on.

Check your game library. If you have the 5 entries Battle Isle, Historyline 1914-1918, Battle Isle 2, Battle Isle 3 and Incubation you should have everything.#

Where do I find my game library? Is that on the main program page?

Move your mouse cursor to your name on the top of the screen, a menu will pop up, then move the cursor down to games.