A little background: I'm running a first-generation Mac Pro with a PCI-Express GPU connector. My card is an ATI Radeon X1900 XT 512 MB. Originally, the card was giving me all kinds of weird artifacts during 3D gaming (World of Warcraft) and after much cajoling over the phone I was able to get Apple to replace the card under warranty. This solved the problem. Now I am running the revised edition of the same card. Flash forward to a year or so ago. Out of nowhere, the computer has begun shutting itself off. It doesn't happen every day. It doesn't even happen every week. I'd say once a month at the worst. But still, out of nowhere it just powers down. In addition, when running pretty much ANY full-screen app, such as a game that involves 3D graphics, the screen simply blanks out while the rest of the computer continues to function. When this behavior began, I took the computer to the genius bar, thinking it was the power unit. They ran tests and the power unit came up peachy. However, I have begun wondering if perhaps it's the GPU that is to blame. I had this problem with my previous computer, a Dell desktop. It would shut the computer down during certain games, and when I bought a new DVI-based LCD monitor to replace my CRT, it fried the connection between the GPU and the logic board and bricked the computer. So after all that, my question is this: Do you think I would be able to solve my issues by replacing/upgrading the GPU? I could theoretically buy a new iMac this summer when they're updated, but I really think my current computer is still filling my needs. I don't really game on it anymore, and after I recently doubled the onboard RAM it really has been able to chug along nicely in performing its other duties. Here is the card I was looking at as a replacement: http://www.macpalace.com/mac-parts/...ation-512-mb-mac-pro-2-2-66-3-ghz-a1186-ma35/ or possibly: http://www.macpalace.com/mac-parts/...card-nvidia-geforce-8800-gt-512-mb-and-cable/ (I'm not sure how they're different) Do you think this would solve the issue? I'd hate to sink another $200 into an old computer and not help things, but if it DOES solve the issues, then I could easily get another 2 years or so out of the computer, which would wind up saving me money since when I DO replace it, I'll get more computer per dollar, PLUS I'll be able to sell this as a functioning computer and not a defect. Thanks.