[Thought]

Ok, try this, I had a similar problem but I can't really know if my problem was the same as yours:

Start -> Settings -> Control Panel

Then go to Display, a new window should appear, titled Display Properties, change to the Settings tab, then press the Advanced button.

A new window, titled (your monitor name) and (your video card name), something like that.

Switch to the tab named after your video card, it's probably named something like GeForce (model name/number).

A new menu should pop out of the side of this window, look for Performance & Quality Settings in the list.

Now, there should be three slider bars, titled Image Settings - (Selected Setting), Antialiasing - (Selected Setting), and Anisotropic Filtering - (Selected Setting).

If the Antialiasing setting is at anything OTHER THAN Off or Application, change it to Off or Application, however, I suggest Application.

If it isn't, then sadly, you do not have my problem that I had.

Attached is a screenshot of the window I am talking about...