Let me just state one caveat to my question. I know my hardware is relatively ancient, but it's all I have. I have a Dell OptiPlex 755 with a Core 2 Quad CPU Q8400. I was running a Nvidia GeForce 6800, and I was able to overclock my Core 2 Quad from 2.6Ghz to 3.0Ghz with almost no CPU temp increase. My old Nvidia bit the dust, and I bought an older Dell ATI Radeon HD 4550, which greatly improved the graphics across the board. But . . . now I can't overclock at all. Nothing changed except for the graphic card swap. Even a 01 increase in frequency crashes the computer. What gives?