Okay, after trying several things suggested online, I feel like I'm getting a grip on the ntdll issue. The thing that seems to have done it, is enabling the Administrator account and playing from there. I read that ntdll errors can be caused by a corrupted user account, which is quite possible as I bought this laptop from a shady second hand shop. First, on the user account, I loaded up a Vikings game from scratch, waited for the autoplay to finish, then began moving around the camera leading to an immediate crash. Then, on the administrator account, I first set up the game settings the exact same way as on the user account, including the 4GB patch and stuff, windowed mode, etc., started another Viking game, playing for a while. Up to this point nothing extraordinary. But when I saved the game, quit civ, then loaded the game up right from the file (normally a sure fire way to get a crash), and immediately began moving the camera around frantically (normally a suicidal move) and... nothing happened. But there was another interesting phenomenon. Where the camera normally either moves smoothly or gets stuck and crashes, on the admin account the camera did neither. Instead, moving the camera around created a kind of "wavy" effect, as if layers of digital pictures were moving over one another. The only other time I had seen this wavy effect was about 12 or 13 years ago, watching a friend play civ on his graphically limited computer. So apparently that is the normal way civ handles camera movement on graphically weak computers. While my computer is able to run vanilla civ 4 smoothly, this is not the case for the much more demanding DoC. I suspect that the ntdll file was somehow involved in producing the wavy effect, and, this file not working properly on a possibly corrupted user account, the game was unable to produce it in order to facilitate camera movement, leading to the crashes.