Hi!
For some strange reason, Graw 2 is just acting strangely. every time I play the game or go onto the menu, there is errors on the screen.(graphical errors) Im talking about lines going all over the screen and such. and when I play the game the errors are crazy. the game plays fine, but random cliffs and lines come up. and after about 2 minutes of gameplay, the screen turns to horizontal lines, and it shuts off. not sure why. I have a brand new HD 4870, with the fan tweak, 2 GB of ram, and dual boot Vista and XP, both do the same. Any help here?

Hi. now I'm not very skilled when it comes to computers but the graphic-problems that you describe look a lot like problems that I have experienced in the past. They were for the full 100% caused by the overclock-settings of my videocard: They were a bit too high. Downclocking solved my problems then.
You didn't say whether you have overclocked anything... so maybe this is not the anwer you were looking for.

Ok. I read the forums and I did downclock the card. all the way actually. down to 500 MHz clock and 810 memory.(which is actually 1810 MHz)I even got the patches lol. I reainstalled it twice on both operating systems. maybe I need to Ultra-downgrade the clocks. or downlock drivers perhaps?

No.. wait for ppl that are able to give better advice than me. (Or post a new thread in which u clearly mention the HD 4870 in 'the headline').