Well, I downloaded the SP (Single Player) Demo available at the official site (as opposed to the "Final Demo" and the "Multiplayer Demo"). This demo runs jerkily and partially slow on Low Detail. I am absolutely sure I exceed the requirements for the low detail setting. I even meet the high detail requirements except for my graphics card (Radeon 7500). What's really strange is that the game runs no more slower or jerkier at high detail than at low detail . I'm wondering if the problem is that I do not have the "Final Demo". Are there any reports of the SP Demo running slower than the "Final Demo" or the actual game? Or should I expect similar results if I were to buy the game?

Thank you. I appreciate your help.