Technical issues in Heroes IV.

I'm talking specifically about Heroes 4.
If it were as simple as you say, I wouldn't be posting my question here. To be more precise, when I try to install it, a window pops up with three options: reinstall, repair, or uninstall, even though the game isn't installed on my computer! I've tried clicking (and repeatedly clicking) "uninstall," but it doesn't help – the same thing happens every time I try to launch it. And if I click "reinstall," it installs to the C drive! That's the problem I'm having. How can I fix it?