Thank you mate!
I have disabled the shadows, allright - no meaning to play otherwise. The game was just barely playeable (with shadows at the minimum) while at the conning tower, but when inside the sub the game CRAWLS! And while they add a lot depth and immersion to the game, gameplay comes before eye candy.
Have to say, it still looks very good without the shadows, but knowing that I could have even more makes me wonder about updating the hardware...
I was aware of the my graphics card's weakness when I bought this computer. But... that's what you get when you don't assemble it yourself!
So, my graphics card sucks enough that I can't turn on the shadows. But what abaout the ropes? Is it Nvidia driver issue, or is it just my machine's problem?