It's probably worth noting that the PC version of Dead Space has some crippling technical problems. If you turn Vsync on, it introduces an incredible amount of input lag - more than it usually does in other games I mean - and the game becomes unplayable. We're talking like nearly a second delay.
However, if you turn Vsync off, the screen tearing is absolutely horrendous (As in, you didn't know it was possible for your screen to tear that bad); and on top of that, it actually breaks the game in such a way that makes it impossible for you to progress. In the beginning of the game, there's a doorway you have to walk through. Leaving Vsync turned off disallows you from actually entering the doorway. You'll just end up hitting an invisible barrier. It's incredibly bizarre.
The only way to get Dead Space to run in a desirable manner is to have Vsync turned off, and use a framerate limiter to limit the game to your monitor's refresh rate. The lower the framerate, the less glitchy the game is (sounds silly, I know). I recommend using D3DOverrider to force triple buffering. Works like a charm.
