I have just downloaded the game (Imperialism 2) onto my windows 10 laptop, and I can only get as far as selecting the country i want to play with, because as soon as a pop-up box appears telling me I can't build my capital in a specific location (for example), I am unable to click on the pop-up box and can't get any further. Can anyone help?

escape closes the boxes,too, does that work?

Thanks for your reply. No that doesn't work for me, just get the pop-up box and however much I click on anything nothing happens. It makes the noise that the click is being recofnised but doesn't actually do anything.

Same issue.
Any ideas how to fix it?

I've had a similar issue and noticed that whenever I started a game a bling sound was heard. Turns out I had a _winCdPlay error messagebox popping up along with my game. The fix for that issue was mounting an iso as others have helpfully pointed out, since Imperialism is looking for a dvd/cd drive. Muting the music and sounds also worked but why would I want to do that? :)

Afterwards I had no more closing issues on pop-up boxes. Hopes this helps someone.