A friend recently built me a system. It is running Snow Leopard 10.6.6 with an i7 Core. I have been warned by my builder that changing anything in the system could mess up my OS and kill the functionality. Now, my video card (Sparkle Nvidia GTX+ 9800 512mB) seems to have taken a dive. It has been difficult to find a replacement because the card is a couple years old. I can find a newer video card with bigger specs, but I am fearful of upgrading after my builder's warnings. Am I stuck with a non-working machine now?